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<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
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      line-height: 1;
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      padding: 2px 7px;
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      margin-bottom: 2px;
      border: 1px solid #bae6fd;
      transition: all 0.3s ease;
    }

    .vector-arrow {
      position: absolute;
      left: calc(18% + 46px);
      bottom: 40px;
      display: flex;
      align-items: center;
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      transform: scaleX(0.7);
      transform-origin: left center;
      transition: all 0.4s ease;
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    .vector-label {
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      left: 18px;
      font-size: 13px;
      font-weight: 700;
      color: #16a34a;
      white-space: nowrap;
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      padding: 1px 6px;
      border-radius: 4px;
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      transition: all 0.3s ease;
    }

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      max-width: 440px;
      margin: 10px 0;
      position: relative;
      height: 94px;
    }

    .step-card {
      position: absolute;
      inset: 0;
      background: #ffffff;
      border: 1.5px solid #e2e8f0;
      border-radius: 12px;
      padding: 10px 14px;
      display: flex;
      flex-direction: column;
      justify-content: center;
      opacity: 0;
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      transform: translateY(6px);
      transition: opacity 0.3s ease, transform 0.3s ease;
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    .step-card.active {
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      transform: translateY(0);
      border-color: #38bdf8;
      box-shadow: 0 4px 12px rgba(56, 189, 248, 0.12);
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      gap: 8px;
      font-size: 18px;
      font-weight: 700;
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    .hl-m { color: #0284c7; }
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    .hl-f { color: #16a34a; }

    /* Controls */
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    }

    .step-tabs {
      display: flex;
      gap: 6px;
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    .tab-btn {
      flex: 1;
      border: 1px solid #cbd5e1;
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    .tab-btn.active {
      background: #0284c7;
      color: #ffffff;
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    .play-btn {
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      height: 34px;
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      justify-content: center;
      border: 1px solid #cbd5e1;
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      border-radius: 8px;
      cursor: pointer;
      font-size: 13px;
      color: #334155;
      transition: all 0.2s ease;
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      box-shadow: 0 0 0 2px #0284c7;
      transform: scale(1.08);
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      box-shadow: 0 0 0 2px #ea580c;
      transform: scale(1.06);
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    body[data-step="2"] .vector-arrow {
      opacity: 1;
      transform: scaleX(1);
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    body[data-step="2"] .runner-wrap {
      transform: translateX(12px);
    }
  </style>
</head>
<body data-step="0">

  
  <div class="scene">
    <div class="accel-tag">a = 4.5 m/s² →</div>
    
    <div class="runner-wrap" id="runner">
      <span class="mass-badge">m = 60 kg</span>
      <span class="runner-emoji">🏃</span>
    </div>

    <div class="vector-arrow" id="vectorArrow">
      <span class="vector-label">F = 270 N</span>
      <div class="vector-line"></div>
      <div class="vector-head"></div>
    </div>

    <div class="track-line"></div>
  </div>

  
  <div class="steps-container">
    
    <div class="step-card active" id="card0">
      <div class="step-header">Step 1 • Values</div>
      <div class="math-row">
        <span><span class="hl-m">m</span> = 60 kg</span>
        <span style="color:#94a3b8;">,</span>
        <span><span class="hl-a">a</span> = 4.5 m/s²</span>
      </div>
    </div>

    
    <div class="step-card" id="card1">
      <div class="step-header">Step 2 • Formula</div>
      <div class="math-row">
        <span class="hl-f">F</span>
        <span>=</span>
        <span class="hl-m">m</span>
        <span>×</span>
        <span class="hl-a">a</span>
      </div>
    </div>

    
    <div class="step-card" id="card2">
      <div class="step-header">Step 3 • Solve</div>
      <div class="math-row">
        <span class="hl-f">F</span>
        <span>=</span>
        <span class="hl-m">60</span>
        <span>×</span>
        <span class="hl-a">4.5</span>
        <span>=</span>
        <span class="hl-f">270 N</span>
      </div>
    </div>
  </div>

  
  <div class="controls">
    <div class="step-tabs">
      <button class="tab-btn active" onclick="setStep(0)">1. Values</button>
      <button class="tab-btn" onclick="setStep(1)">2. Formula</button>
      <button class="tab-btn" onclick="setStep(2)">3. Solve</button>
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</body>
</html>

Newton's Second Law: Force, Mass, and Acceleration Calculations

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    }

    body {
      background: transparent;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      gap: 12px;
      justify-content: center;
      min-height: 100%;
    }

    .cards-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
      width: 100%;
    }

    @media (max-width: 480px) {
      .cards-grid {
        grid-template-columns: 1fr;
        gap: 10px;
      }
    }

    .calc-card {
      background: #ffffff;
      border: 1.5px solid #e2e8f0;
      border-radius: 14px;
      padding: 14px 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 10px;
    }

    .card-header {
      display: flex;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      padding-bottom: 6px;
      border-bottom: 1px solid #f1f5f9;
    }

    .icon-badge {
      font-size: 26px;
      line-height: 1;
    }

    .formula-tag {
      font-size: 15px;
      font-weight: 700;
      padding: 3px 8px;
      border-radius: 6px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
    }

    /* Color Coded Physics Quantities */
    .f-color { color: #2563eb; } /* Force: Blue */
    .m-color { color: #d97706; } /* Mass: Amber */
    .a-color { color: #059669; } /* Acceleration: Green */

    .values-row {
      display: flex;
      gap: 8px;
      justify-content: center;
      font-size: 13px;
      font-weight: 600;
    }

    .val-chip {
      padding: 2px 7px;
      border-radius: 6px;
      background: #f8fafc;
    }

    /* Clean Fraction Display */
    .equation-box {
      display: flex;
      align-items: center;
      gap: 8px;
      font-size: 18px;
      font-weight: 700;
      padding: 6px 10px;
      background: #f8fafc;
      border-radius: 10px;
      width: 100%;
      justify-content: center;
    }

    .fraction {
      display: inline-flex;
      flex-direction: column;
      align-items: center;
      vertical-align: middle;
      font-size: 14px;
      line-height: 1.1;
    }

    .numerator {
      border-bottom: 2px solid #1e2945;
      padding: 0 4px 2px 4px;
      text-align: center;
      width: 100%;
    }

    .denominator {
      padding: 2px 4px 0 4px;
      text-align: center;
      width: 100%;
    }

    .result-box {
      font-size: 18px;
      font-weight: 800;
      padding: 6px 14px;
      border-radius: 8px;
      display: flex;
      align-items: center;
      gap: 4px;
      width: 100%;
      justify-content: center;
    }

    .res-green {
      background: #ecfdf5;
      border: 1.5px solid #a7f3d0;
    }

    .res-amber {
      background: #fffbeb;
      border: 1.5px solid #fde68a;
    }

    .unit {
      font-size: 14px;
      font-weight: 600;
      opacity: 0.9;
    }
  </style>
</head>
<body>

  <div class="cards-grid">
    
    <div class="calc-card">
      <div class="card-header">
        <span class="icon-badge">🛰️</span>
        <div class="formula-tag">
          <span class="a-color">a</span> = <span class="f-color">F</span> / <span class="m-color">m</span>
        </div>
      </div>

      <div class="values-row">
        <span class="val-chip f-color">F = 1600 N</span>
        <span class="val-chip m-color">m = 800 kg</span>
      </div>

      <div class="equation-box">
        <span class="a-color">a</span>
        <span>=</span>
        <div class="fraction">
          <span class="numerator f-color">1600 N</span>
          <span class="denominator m-color">800 kg</span>
        </div>
      </div>

      <div class="result-box res-green a-color">
        <span>a = 2</span>
        <span class="unit">m/s²</span>
      </div>
    </div>

    
    <div class="calc-card">
      <div class="card-header">
        <span class="icon-badge">🚁</span>
        <div class="formula-tag">
          <span class="m-color">m</span> = <span class="f-color">F</span> / <span class="a-color">a</span>
        </div>
      </div>

      <div class="values-row">
        <span class="val-chip f-color">F = 30 N</span>
        <span class="val-chip a-color">a = 6 m/s²</span>
      </div>

      <div class="equation-box">
        <span class="m-color">m</span>
        <span>=</span>
        <div class="fraction">
          <span class="numerator f-color">30 N</span>
          <span class="denominator a-color">6 m/s²</span>
        </div>
      </div>

      <div class="result-box res-amber m-color">
        <span>m = 5</span>
        <span class="unit">kg</span>
      </div>
    </div>
  </div>

</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <title>Newton's Second Law Free Body Diagram</title>
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    * { box-sizing: border-box; margin: 0; padding: 0; }
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      color: #1e2945;
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      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 12px;
    }

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      display: flex;
      gap: 6px;
      width: 100%;
      max-width: 480px;
      justify-content: center;
      margin-bottom: 8px;
    }

    .step-btn {
      flex: 1;
      padding: 6px 10px;
      font-size: 13px;
      font-weight: 600;
      border: 1px solid #e2e8f0;
      background: #f8fafc;
      color: #64748b;
      border-radius: 6px;
      cursor: pointer;
      transition: all 0.2s ease;
      text-align: center;
    }

    .step-btn.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
    }

    .scene-container {
      position: relative;
      width: 100%;
      max-width: 520px;
      height: 220px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    svg {
      width: 100%;
      height: 100%;
      overflow: visible;
    }

    .calc-card {
      width: 100%;
      max-width: 480px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 10px 14px;
      text-align: center;
      min-height: 56px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 4px;
    }

    .calc-main {
      font-size: 15px;
      font-weight: 700;
      color: #0f172a;
      letter-spacing: -0.2px;
    }

    .calc-sub {
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
    }

    .highlight-net { color: #0284c7; }
    .highlight-thrust { color: #16a34a; }
    .highlight-friction { color: #dc2626; }
    .highlight-accel { color: #7c3aed; }

    .fade-elem {
      transition: opacity 0.3s ease, transform 0.3s ease;
    }

    .hidden {
      opacity: 0;
      pointer-events: none;
    }
  </style>
</head>
<body>

  
  <div class="nav-bar">
    <button class="step-btn active" onclick="setStep(0)">1. Forces</button>
    <button class="step-btn" onclick="setStep(1)">2. Net Force</button>
    <button class="step-btn" onclick="setStep(2)">3. Acceleration</button>
  </div>

  
  <div class="scene-container">
    <svg viewBox="0 0 520 220">
      <defs>
        
        <marker id="arrow-green" markerWidth="8" markerHeight="8" refX="6" refY="4" orient="auto">
          <polygon points="0 1, 7 4, 0 7" fill="#16a34a" />
        </marker>
        <marker id="arrow-red" markerWidth="8" markerHeight="8" refX="2" refY="4" orient="auto-start-reverse">
          <polygon points="7 1, 0 4, 7 7" fill="#dc2626" />
        </marker>
        <marker id="arrow-blue" markerWidth="8" markerHeight="8" refX="6" refY="4" orient="auto">
          <polygon points="0 1, 7 4, 0 7" fill="#0284c7" />
        </marker>
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          <polygon points="0 1, 7 4, 0 7" fill="#7c3aed" />
        </marker>
      </defs>

      
      <line x1="20" y1="165" x2="500" y2="165" stroke="#cbd5e1" stroke-width="3" stroke-dasharray="8 6" />

      
      <g id="car-group" transform="translate(200, 85)">
        
        <path d="M 10 50 L 25 25 Q 35 15 50 15 L 80 15 Q 95 15 105 28 L 115 50 Z" fill="#3b82f6" />
        <rect x="0" y="45" width="125" height="20" rx="6" fill="#1d4ed8" />
        
        <polygon points="32 25, 48 20, 58 20, 58 43, 23 43" fill="#bae6fd" opacity="0.9" />
        <polygon points="64 20, 78 20, 95 28, 102 43, 64 43" fill="#bae6fd" opacity="0.9" />
        
        <circle cx="28" cy="65" r="12" fill="#334155" />
        <circle cx="28" cy="65" r="5" fill="#e2e8f0" />
        <circle cx="96" cy="65" r="12" fill="#334155" />
        <circle cx="96" cy="65" r="5" fill="#e2e8f0" />
        
        <rect x="32" y="48" width="60" height="15" rx="3" fill="#ffffff" opacity="0.95" />
        <text x="62" y="59" font-size="10" font-weight="700" fill="#1e2945" text-anchor="middle">m = 1200 kg</text>
      </g>

      
      <g id="layer-forces" class="fade-elem">
        
        <line x1="190" y1="135" x2="135" y2="135" stroke="#dc2626" stroke-width="4" marker-end="url(#arrow-red)" />
        <rect x="52" y="112" width="128" height="22" rx="4" fill="#fee2e2" stroke="#fca5a5" stroke-width="1" />
        <text x="116" y="127" font-size="11" font-weight="700" fill="#dc2626" text-anchor="middle">Friction = 1400 N</text>

        
        <line x1="330" y1="135" x2="475" y2="135" stroke="#16a34a" stroke-width="4" marker-end="url(#arrow-green)" />
        <rect x="345" y="112" width="125" height="22" rx="4" fill="#dcfce7" stroke="#86efac" stroke-width="1" />
        <text x="407" y="127" font-size="11" font-weight="700" fill="#16a34a" text-anchor="middle">Thrust = 5000 N</text>
      </g>

      
      <g id="layer-net" class="fade-elem hidden">
        
        <line x1="260" y1="42" x2="385" y2="42" stroke="#0284c7" stroke-width="4" marker-end="url(#arrow-blue)" />
        <rect x="270" y="15" width="135" height="22" rx="4" fill="#e0f2fe" stroke="#7dd3fc" stroke-width="1" />
        <text x="337" y="30" font-size="11" font-weight="700" fill="#0284c7" text-anchor="middle">F_net = 3600 N →</text>
      </g>

      
      <g id="layer-accel" class="fade-elem hidden">
        
        <line x1="260" y1="42" x2="385" y2="42" stroke="#7c3aed" stroke-width="4" marker-end="url(#arrow-purple)" />
        <rect x="270" y="15" width="135" height="22" rx="4" fill="#f3e8ff" stroke="#d8b4fe" stroke-width="1" />
        <text x="337" y="30" font-size="11" font-weight="700" fill="#7c3aed" text-anchor="middle">a = 3 m/s² →</text>
      </g>
    </svg>
  </div>

  
  <div class="calc-card">
    <div id="calc-main" class="calc-main">
      Opposing Forces: <span class="highlight-thrust">5000 N</span> vs <span class="highlight-friction">1400 N</span>
    </div>
    <div id="calc-sub" class="calc-sub">
      Thrust pushes forward, Friction opposes backward
    </div>
  </div>

  <script>
    const steps = [
      {
        forces: true,
        net: false,
        accel: false,
        main: 'Opposing Forces: <span class="highlight-thrust">5000 N</span> vs <span class="highlight-friction">1400 N</span>',
        sub: 'Thrust pushes right, Friction resists left'
      },
      {
        forces: true,
        net: true,
        accel: false,
        main: 'Net Force: <span class="highlight-thrust">5000 N</span> − <span class="highlight-friction">1400 N</span> = <span class="highlight-net">3600 N →</span>',
        sub: 'F_net = Forward Force − Opposing Force'
      },
      {
        forces: false,
        net: false,
        accel: true,
        main: 'Acceleration: <span class="highlight-net">3600 N</span> ÷ 1200 kg = <span class="highlight-accel">3 m/s² →</span>',
        sub: 'a = F ÷ m (Newton\'s Second Law)'
      }
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      const data = steps[currentStep];

      // Toggle SVG Layers
      document.getElementById('layer-forces').classList.toggle('hidden', !data.forces);
      document.getElementById('layer-net').classList.toggle('hidden', !data.net);
      document.getElementById('layer-accel').classList.toggle('hidden', !data.accel);

      // Update text
      document.getElementById('calc-main').innerHTML = data.main;
      document.getElementById('calc-sub').innerHTML = data.sub;

      // Update buttons
      const btns = document.querySelectorAll('.step-btn');
      btns.forEach((btn, idx) => {
        btn.classList.toggle('active', idx === currentStep);
      });
    }

    function setStep(index) {
      currentStep = index;
      renderStep();
      resetTimer();
    }

    function nextStep() {
      currentStep = (currentStep + 1) % steps.length;
      renderStep();
    }

    function resetTimer() {
      if (autoInterval) clearInterval(autoInterval);
      autoInterval = setInterval(nextStep, 3800);
    }

    // Initialize
    renderStep();
    resetTimer();
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      background: #ffffff;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      padding: 12px 10px 8px;
      user-select: none;
    }

    .comparison-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
      width: 100%;
      max-width: 620px;
    }

    .column {
      display: flex;
      flex-direction: column;
      align-items: center;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px 8px 10px;
      position: relative;
    }

    .column-header {
      font-size: 13px;
      font-weight: 700;
      color: #334155;
      margin-bottom: 2px;
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .column-header .badge {
      font-size: 10px;
      font-weight: 600;
      padding: 1px 6px;
      border-radius: 4px;
      text-transform: uppercase;
      letter-spacing: 0.3px;
    }
    .badge-a { background: #e0f2fe; color: #0284c7; }
    .badge-b { background: #e2e8f0; color: #475569; }

    .track-area {
      width: 100%;
      height: 105px;
      position: relative;
      overflow: hidden;
      display: flex;
      align-items: flex-end;
      padding-bottom: 6px;
    }

    .floor-line {
      position: absolute;
      bottom: 6px;
      left: 0;
      right: 0;
      height: 2px;
      background: #cbd5e1;
    }

    .box-wrapper {
      position: absolute;
      bottom: 8px;
      left: 12px;
      display: flex;
      align-items: center;
      transition: transform 1.2s cubic-bezier(0.25, 1, 0.5, 1);
    }

    /* Force Arrow */
    .force-arrow {
      display: flex;
      align-items: center;
      margin-right: 6px;
      color: #0284c7;
      font-size: 11px;
      font-weight: 700;
    }

    .arrow-shaft {
      width: 30px;
      height: 4px;
      background: #0284c7;
      position: relative;
    }
    .arrow-head {
      width: 0;
      height: 0;
      border-top: 5px solid transparent;
      border-bottom: 5px solid transparent;
      border-left: 7px solid #0284c7;
    }

    .force-label {
      position: absolute;
      top: -15px;
      left: 0;
      white-space: nowrap;
      font-size: 11px;
    }

    /* Boxes */
    .box-a {
      width: 42px;
      height: 42px;
      background: #38bdf8;
      border: 2px solid #0284c7;
      border-radius: 6px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      color: #0c4a6e;
      font-weight: 700;
      font-size: 12px;
      box-shadow: 0 2px 4px rgba(0,0,0,0.08);
    }

    .box-b {
      width: 62px;
      height: 62px;
      background: #94a3b8;
      border: 2px solid #475569;
      border-radius: 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      color: #0f172a;
      font-weight: 700;
      font-size: 13px;
      box-shadow: 0 2px 4px rgba(0,0,0,0.08);
    }

    /* Motion Lines */
    .motion-lines {
      position: absolute;
      left: -18px;
      top: 50%;
      transform: translateY(-50%);
      opacity: 0;
      transition: opacity 0.3s ease;
      pointer-events: none;
    }

    .motion-line {
      height: 2px;
      background: #94a3b8;
      border-radius: 1px;
      margin: 3px 0;
    }

    .line-long { width: 24px; }
    .line-med { width: 14px; margin-left: 5px; }
    .line-short { width: 8px; }

    /* Animated states */
    .moving.box-a-wrap {
      transform: translateX(110px);
    }
    .moving.box-b-wrap {
      transform: translateX(20px);
    }
    .moving .motion-lines {
      opacity: 1;
    }

    /* Speedometer Gauge */
    .gauge-container {
      width: 110px;
      height: 68px;
      position: relative;
      margin-top: 4px;
      display: flex;
      flex-direction: column;
      align-items: center;
    }

    .gauge-svg {
      width: 110px;
      height: 56px;
    }

    .gauge-needle {
      transform-origin: 60px 58px;
      transform: rotate(-90deg);
      transition: transform 1.2s cubic-bezier(0.2, 0.8, 0.3, 1);
    }

    .accel-val {
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
      margin-top: -6px;
    }

    .accel-tag {
      font-size: 10px;
      font-weight: 600;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      padding: 1px 6px;
      border-radius: 4px;
      margin-top: 2px;
    }

    .tag-high { background: #e0f2fe; color: #0369a1; }
    .tag-low { background: #f1f5f9; color: #475569; }

    /* Control Button */
    .controls {
      margin-top: 10px;
      display: flex;
      gap: 10px;
    }

    .push-btn {
      background: #0284c7;
      color: #ffffff;
      border: none;
      border-radius: 18px;
      padding: 7px 20px;
      font-size: 12px;
      font-weight: 600;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 6px;
      box-shadow: 0 2px 4px rgba(2, 132, 199, 0.25);
      transition: background 0.2s ease;
    }

    .push-btn:hover {
      background: #0369a1;
    }

    .push-btn:active {
      background: #075985;
    }

    /* Responsive Stacking for Mobile */
    @media (max-width: 500px) {
      body {
        padding: 8px;
      }
      .comparison-grid {
        grid-template-columns: 1fr;
        gap: 8px;
      }
      .column {
        flex-direction: row;
        justify-content: space-between;
        align-items: center;
        padding: 8px 12px;
        flex-wrap: wrap;
      }
      .column-header {
        width: 100%;
        margin-bottom: 4px;
      }
      .track-area {
        width: calc(100% - 120px);
        height: 85px;
      }
      .gauge-container {
        width: 105px;
        height: 64px;
        margin-top: 0;
      }
      .gauge-svg {
        width: 105px;
        height: 52px;
      }
      .box-b {
        width: 54px;
        height: 54px;
      }
      .box-a {
        width: 38px;
        height: 38px;
      }
      .moving.box-a-wrap {
        transform: translateX(80px);
      }
      .moving.box-b-wrap {
        transform: translateX(16px);
      }
      .controls {
        margin-top: 8px;
      }
    }
  </style>
</head>
<body>

  <div class="comparison-grid">
    
    <div class="column">
      <div class="column-header">
        <span>Box A (Light)</span>
        <span class="badge badge-a">5 kg</span>
      </div>
      <div class="track-area">
        <div class="floor-line"></div>
        <div class="box-wrapper box-a-wrap" id="boxWrapA">
          <div class="motion-lines">
            <div class="motion-line line-long"></div>
            <div class="motion-line line-med"></div>
            <div class="motion-line line-long"></div>
          </div>
          <div class="force-arrow">
            <div class="force-label">20 N</div>
            <div class="arrow-shaft"></div>
            <div class="arrow-head"></div>
          </div>
          <div class="box-a">
            <span>5 kg</span>
          </div>
        </div>
      </div>

      
      <div class="gauge-container">
        <svg class="gauge-svg" viewBox="0 0 120 65">
          
          <path d="M 15 58 A 45 45 0 0 1 105 58" fill="none" stroke="#e2e8f0" stroke-width="8" stroke-linecap="round" />
          
          <path d="M 15 58 A 45 45 0 0 1 105 58" fill="none" stroke="#38bdf8" stroke-width="8" stroke-dasharray="141" stroke-dashoffset="30" stroke-linecap="round" />
          
          <g class="gauge-needle" id="needleA">
            <line x1="60" y1="58" x2="60" y2="20" stroke="#0369a1" stroke-width="3" stroke-linecap="round" />
            <circle cx="60" cy="58" r="4" fill="#0369a1" />
          </g>
        </svg>
        <div class="accel-val">4.0 m/s²</div>
        <span class="accel-tag tag-high">High Accel</span>
      </div>
    </div>

    
    <div class="column">
      <div class="column-header">
        <span>Box B (Heavy)</span>
        <span class="badge badge-b">50 kg</span>
      </div>
      <div class="track-area">
        <div class="floor-line"></div>
        <div class="box-wrapper box-b-wrap" id="boxWrapB">
          <div class="motion-lines">
            <div class="motion-line line-short"></div>
            <div class="motion-line line-short"></div>
          </div>
          <div class="force-arrow">
            <div class="force-label">20 N</div>
            <div class="arrow-shaft"></div>
            <div class="arrow-head"></div>
          </div>
          <div class="box-b">
            <span>50 kg</span>
          </div>
        </div>
      </div>

      
      <div class="gauge-container">
        <svg class="gauge-svg" viewBox="0 0 120 65">
          
          <path d="M 15 58 A 45 45 0 0 1 105 58" fill="none" stroke="#e2e8f0" stroke-width="8" stroke-linecap="round" />
          
          <path d="M 15 58 A 45 45 0 0 1 35 30" fill="none" stroke="#94a3b8" stroke-width="8" stroke-linecap="round" />
          
          <g class="gauge-needle" id="needleB">
            <line x1="60" y1="58" x2="60" y2="20" stroke="#475569" stroke-width="3" stroke-linecap="round" />
            <circle cx="60" cy="58" r="4" fill="#475569" />
          </g>
        </svg>
        <div class="accel-val">0.4 m/s²</div>
        <span class="accel-tag tag-low">Low Accel</span>
      </div>
    </div>
  </div>

  <div class="controls">
    <button class="push-btn" id="pushBtn">▶ Push Both (20 N)</button>
  </div>

  <script>
    const boxA = document.getElementById('boxWrapA');
    const boxB = document.getElementById('boxWrapB');
    const needleA = document.getElementById('needleA');
    const needleB = document.getElementById('needleB');
    const pushBtn = document.getElementById('pushBtn');

    let isPushed = false;
    let autoTimer = null;

    function applyPush(state) {
      isPushed = state;
      if (isPushed) {
        boxA.classList.add('moving');
        boxB.classList.add('moving');
        needleA.style.transform = 'rotate(54deg)';
        needleB.style.transform = 'rotate(-75deg)';
        pushBtn.textContent = '↺ Reset';
      } else {
        boxA.classList.remove('moving');
        boxB.classList.remove('moving');
        needleA.style.transform = 'rotate(-90deg)';
        needleB.style.transform = 'rotate(-90deg)';
        pushBtn.textContent = '▶ Push Both (20 N)';
      }
    }

    pushBtn.addEventListener('click', () => {
      clearInterval(autoTimer);
      applyPush(!isPushed);
    });

    // Auto-demo cycle on mount
    setTimeout(() => {
      applyPush(true);
      autoTimer = setInterval(() => {
        applyPush(!isPushed);
      }, 3000);
    }, 400);
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <title>Newton's Second Law: F = ma</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: #ffffff;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
    }

    .toolbar {
      display: flex;
      gap: 8px;
      margin-bottom: 12px;
      width: 100%;
      max-width: 520px;
      justify-content: center;
    }

    .btn-var {
      flex: 1;
      padding: 8px 10px;
      font-size: 14px;
      font-weight: 700;
      border: 2px solid transparent;
      border-radius: 8px;
      background: #f1f5f9;
      color: #64748b;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      transition: all 0.2s ease;
      user-select: none;
    }

    .btn-var.active-F {
      background: #eff6ff;
      border-color: #0284c7;
      color: #0284c7;
      box-shadow: 0 2px 6px rgba(2, 132, 199, 0.2);
    }
    .btn-var.active-m {
      background: #fff7ed;
      border-color: #ea580c;
      color: #ea580c;
      box-shadow: 0 2px 6px rgba(234, 88, 12, 0.2);
    }
    .btn-var.active-a {
      background: #f0fdf4;
      border-color: #16a34a;
      color: #16a34a;
      box-shadow: 0 2px 6px rgba(22, 163, 74, 0.2);
    }

    .main-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
      width: 100%;
      max-width: 520px;
      align-items: stretch;
    }

    @media (max-width: 440px) {
      .main-grid {
        grid-template-columns: 1fr;
        gap: 10px;
      }
    }

    .panel {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
    }

    /* Equation Display */
    .formula-display {
      font-size: 28px;
      font-weight: 800;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      margin-bottom: 8px;
      min-height: 52px;
    }

    .fraction {
      display: inline-flex;
      flex-direction: column;
      align-items: center;
      vertical-align: middle;
      font-size: 0.9em;
      line-height: 1;
    }
    .frac-num {
      border-bottom: 2px solid #1e2945;
      padding: 0 6px 2px 6px;
      width: 100%;
      text-align: center;
    }
    .frac-den {
      padding: 2px 6px 0 6px;
      width: 100%;
      text-align: center;
    }

    .unit-tag {
      font-size: 13px;
      font-weight: 600;
      padding: 4px 10px;
      border-radius: 20px;
      background: #ffffff;
      border: 1px solid #cbd5e1;
      color: #475569;
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .color-F { color: #0284c7; }
    .color-m { color: #ea580c; }
    .color-a { color: #16a34a; }

    /* SVG Triangle */
    .triangle-box {
      width: 100%;
      max-width: 220px;
      aspect-ratio: 1.15;
      position: relative;
    }
    svg {
      width: 100%;
      height: 100%;
      overflow: visible;
      user-select: none;
    }

    .tri-sector {
      cursor: pointer;
      transition: opacity 0.2s ease, fill 0.2s ease;
    }
    .tri-sector:hover {
      filter: brightness(0.96);
    }
    .tri-text {
      font-size: 24px;
      font-weight: 800;
      dominant-baseline: central;
      text-anchor: middle;
      pointer-events: none;
    }
    .tri-unit {
      font-size: 11px;
      font-weight: 600;
      dominant-baseline: central;
      text-anchor: middle;
      pointer-events: none;
      fill: #64748b;
    }
    .op-symbol {
      font-size: 16px;
      font-weight: 800;
      fill: #94a3b8;
      dominant-baseline: central;
      text-anchor: middle;
      pointer-events: none;
    }

    .cover-highlight {
      transition: all 0.25s ease;
      pointer-events: none;
    }
  </style>
</head>
<body>

  <div class="toolbar">
    <button class="btn-var active-F" id="btn-F" onclick="selectVar('F')">Find F (Force)</button>
    <button class="btn-var" id="btn-m" onclick="selectVar('m')">Find m (Mass)</button>
    <button class="btn-var" id="btn-a" onclick="selectVar('a')">Find a (Accel)</button>
  </div>

  <div class="main-grid">
    
    <div class="panel">
      <div class="formula-display" id="formulaBox">
        <span class="color-F">F</span>
        <span>=</span>
        <span class="color-m">m</span>
        <span>&times;</span>
        <span class="color-a">a</span>
      </div>
      <div class="unit-tag" id="unitBox">
        <span class="color-F" style="font-weight:700;">Newtons [N]</span>
      </div>
    </div>

    
    <div class="panel">
      <div class="triangle-box">
        <svg viewBox="0 0 200 174">
          
          <polygon points="100,8 195,168 5,168" fill="#ffffff" stroke="#cbd5e1" stroke-width="2" stroke-linejoin="round"/>
          
          
          <polygon id="sec-F" class="tri-sector" points="100,10 148,90 52,90" fill="#f0f9ff" onclick="selectVar('F')"/>
          
          <polygon id="sec-m" class="tri-sector" points="52,90 100,90 100,166 6,166" fill="#fff7ed" onclick="selectVar('m')"/>
          
          <polygon id="sec-a" class="tri-sector" points="100,90 148,90 194,166 100,166" fill="#f0fdf4" onclick="selectVar('a')"/>

          
          <line x1="52" y1="90" x2="148" y2="90" stroke="#94a3b8" stroke-width="2.5" stroke-linecap="round"/>
          <line x1="100" y1="90" x2="100" y2="166" stroke="#94a3b8" stroke-width="2.5" stroke-linecap="round"/>

          
          <text x="36" y="80" class="op-symbol">&divide;</text>
          <text x="164" y="80" class="op-symbol">&divide;</text>
          <text x="100" y="128" class="op-symbol">&times;</text>

          
          <text x="100" y="46" class="tri-text color-F" fill="#0284c7">F</text>
          <text x="100" y="66" class="tri-unit">[N]</text>

          <text x="56" y="124" class="tri-text color-m" fill="#ea580c">m</text>
          <text x="56" y="144" class="tri-unit">[kg]</text>

          <text x="144" y="124" class="tri-text color-a" fill="#16a34a">a</text>
          <text x="144" y="144" class="tri-unit">[m/s&sup2;]</text>

          
          <circle id="coverRing" class="cover-highlight" cx="100" cy="53" r="32" fill="none" stroke="#0284c7" stroke-width="3" stroke-dasharray="4,4"/>
        </svg>
      </div>
    </div>
  </div>

  <script>
    const data = {
      F: {
        formula: '<span class="color-F">F</span> <span>=</span> <span class="color-m">m</span> <span>&times;</span> <span class="color-a">a</span>',
        unit: '<span class="color-F" style="font-weight:700;">Resultant Force [N]</span>',
        ringPos: { cx: 100, cy: 53, r: 33, stroke: '#0284c7' }
      },
      m: {
        formula: '<span class="color-m">m</span> <span>=</span> <div class="fraction"><span class="frac-num color-F">F</span><span class="frac-den color-a">a</span></div>',
        unit: '<span class="color-m" style="font-weight:700;">Mass [kg]</span>',
        ringPos: { cx: 56, cy: 130, r: 30, stroke: '#ea580c' }
      },
      a: {
        formula: '<span class="color-a">a</span> <span>=</span> <div class="fraction"><span class="frac-num color-F">F</span><span class="frac-den color-m">m</span></div>',
        unit: '<span class="color-a" style="font-weight:700;">Acceleration [m/s&sup2;]</span>',
        ringPos: { cx: 144, cy: 130, r: 30, stroke: '#16a34a' }
      }
    };

    function selectVar(v) {
      // Update Buttons
      document.getElementById('btn-F').className = 'btn-var' + (v === 'F' ? ' active-F' : '');
      document.getElementById('btn-m').className = 'btn-var' + (v === 'm' ? ' active-m' : '');
      document.getElementById('btn-a').className = 'btn-var' + (v === 'a' ? ' active-a' : '');

      // Update Formula and Unit
      document.getElementById('formulaBox').innerHTML = data[v].formula;
      document.getElementById('unitBox').innerHTML = data[v].unit;

      // Update SVG Highlight Ring
      const ring = document.getElementById('coverRing');
      ring.setAttribute('cx', data[v].ringPos.cx);
      ring.setAttribute('cy', data[v].ringPos.cy);
      ring.setAttribute('r', data[v].ringPos.r);
      ring.setAttribute('stroke', data[v].ringPos.stroke);

      // Dim non-selected sectors slightly
      document.getElementById('sec-F').style.opacity = (v === 'F' ? '1' : '0.5');
      document.getElementById('sec-m').style.opacity = (v === 'm' ? '1' : '0.5');
      document.getElementById('sec-a').style.opacity = (v === 'a' ? '1' : '0.5');
    }

    // Initialize default state
    selectVar('F');
  </script>
</body>
</html>

UK-GCSE-SCIENCE-PHYS-FM-02-02

Aligned learning resources

Related diagrams