<!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="1:1">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    html, body {
      width: 100%;
      height: 100%;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: #ffffff;
      color: #1e293b;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      user-select: none;
      -webkit-user-select: none;
    }

    .top-bar {
      width: 100%;
      display: flex;
      justify-content: center;
      padding: 8px 12px 4px;
    }

    .formula-card {
      display: inline-flex;
      align-items: center;
      gap: 8px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 9999px;
      padding: 5px 14px;
      font-size: 13px;
      font-weight: 600;
      color: #0f172a;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
    }

    .formula-eq {
      font-family: 'Times New Roman', Times, serif;
      font-size: 15px;
      font-style: italic;
      letter-spacing: 0.5px;
    }

    .unit-tag {
      font-size: 11px;
      font-weight: 500;
      color: #64748b;
      background: #edf2f7;
      padding: 2px 6px;
      border-radius: 4px;
    }

    .svg-wrap {
      width: 100%;
      flex: 1;
      min-height: 0;
      display: flex;
      align-items: center;
      justify-content: center;
      position: relative;
    }

    svg {
      width: 100%;
      height: 100%;
      max-width: 400px;
      max-height: 400px;
    }

    /* Controls */
    .controls {
      display: flex;
      gap: 6px;
      padding: 4px 12px 10px;
    }

    .btn-step {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 8px;
      padding: 6px 14px;
      font-size: 13px;
      font-weight: 600;
      color: #334155;
      cursor: pointer;
      transition: all 0.2s ease;
    }

    .btn-step.active {
      background: #1e3a8a;
      border-color: #1e3a8a;
      color: #ffffff;
      box-shadow: 0 2px 4px rgba(30, 58, 138, 0.2);
    }

    .ring-line {
      fill: none;
      stroke: #cbd5e1;
      stroke-width: 1.2;
      stroke-dasharray: 4 4;
      transition: stroke 0.3s ease, stroke-width 0.3s ease;
    }

    .ring-line.active {
      stroke: #2563eb;
      stroke-width: 2;
      stroke-dasharray: none;
    }

    .arrow {
      transition: opacity 0.3s ease;
    }

    .dimmed {
      opacity: 0.25;
    }
  </style>
</head>
<body>

  <div class="top-bar">
    <div class="formula-card">
      <span class="formula-eq">g = GM / r²</span>
      <span class="unit-tag">N/kg</span>
    </div>
  </div>

  <div class="svg-wrap">
    <svg viewBox="0 0 360 360" id="fieldSvg">
      <defs>
        
        <radialGradient id="earthGrad" cx="40%" cy="40%" r="60%">
          <stop offset="0%" stop-color="#3b82f6" />
          <stop offset="60%" stop-color="#1e3a8a" />
          <stop offset="100%" stop-color="#0f172a" />
        </radialGradient>
      </defs>

      
      <g id="ringsGroup">
        <circle id="ring3" class="ring-line" cx="180" cy="180" r="150" />
        <circle id="ring2" class="ring-line" cx="180" cy="180" r="105" />
        <circle id="ring1" class="ring-line" cx="180" cy="180" r="60" />
      </g>

      
      <g fill="#64748b" font-size="11" font-weight="600" text-anchor="middle" font-family="system-ui">
        <text x="240" y="174">1r</text>
        <text x="285" y="174">2r</text>
        <text x="330" y="174">3r</text>
      </g>

      
      <g id="vectorsGroup"></g>

      
      <circle cx="180" cy="180" r="28" fill="url(#earthGrad)" stroke="#1e293b" stroke-width="1.5" />
      <text x="180" y="185" text-anchor="middle" fill="#ffffff" font-size="14" font-weight="bold" font-family="'Times New Roman', serif" font-style="italic">M</text>

      
      <g id="badgeGroup" transform="translate(18, 320)">
        <rect width="104" height="24" rx="6" fill="#f8fafc" stroke="#e2e8f0" stroke-width="1" />
        <text id="strengthText" x="52" y="16" text-anchor="middle" font-size="11" font-weight="700" fill="#1e3a8a">g = 1 g₀</text>
      </g>
    </svg>
  </div>

  <div class="controls">
    <button class="btn-step active" onclick="setRadius(1)">r (1×)</button>
    <button class="btn-step" onclick="setRadius(2)">2r (¼×)</button>
    <button class="btn-step" onclick="setRadius(3)">3r (⅑×)</button>
  </div>

  <script>
    const cx = 180, cy = 180;
    const angles = [0, 45, 90, 135, 180, 225, 270, 315];
    const group = document.getElementById('vectorsGroup');

    // Vector definitions:
    // Level 1: r=60, len=28, dark blue
    // Level 2: r=105, len=7 (28/4), medium blue
    // Level 3: r=150, len=3.1 (28/9), light blue
    const levels = [
      { r: 60,  len: 26, color: '#1e3a8a', width: 2.2, head: 7, level: 1 },
      { r: 105, len: 6.5, color: '#3b82f6', width: 1.8, head: 5, level: 2 },
      { r: 150, len: 2.9, color: '#93c5fd', width: 1.4, head: 3.5, level: 3 }
    ];

    function drawField() {
      group.innerHTML = '';
      levels.forEach(lvl => {
        angles.forEach(deg => {
          const rad = (deg * Math.PI) / 180;
          // Vector starts at lvl.r and points inward toward center
          const startX = cx + Math.cos(rad) * lvl.r;
          const startY = cy + Math.sin(rad) * lvl.r;
          const endX = cx + Math.cos(rad) * (lvl.r - lvl.len);
          const endY = cy + Math.sin(rad) * (lvl.r - lvl.len);

          // Arrow line
          const line = document.createElementNS('http://www.w3.org/2000/svg', 'line');
          line.setAttribute('x1', startX);
          line.setAttribute('y1', startY);
          line.setAttribute('x2', endX);
          line.setAttribute('y2', endY);
          line.setAttribute('stroke', lvl.color);
          line.setAttribute('stroke-width', lvl.width);
          line.setAttribute('stroke-linecap', 'round');
          line.setAttribute('class', `arrow arrow-lvl-${lvl.level}`);

          // Inward pointing arrowhead
          const headAngle = Math.PI / 6;
          const hLen = lvl.head;
          const tipAngle = rad + Math.PI; // pointing towards center
          
          const a1X = endX + hLen * Math.cos(rad + headAngle);
          const a1Y = endY + hLen * Math.sin(rad + headAngle);
          const a2X = endX + hLen * Math.cos(rad - headAngle);
          const a2Y = endY + hLen * Math.sin(rad - headAngle);

          const head = document.createElementNS('http://www.w3.org/2000/svg', 'polygon');
          head.setAttribute('points', `${endX},${endY} ${a1X},${a1Y} ${a2X},${a2Y}`);
          head.setAttribute('fill', lvl.color);
          head.setAttribute('class', `arrow arrow-lvl-${lvl.level}`);

          group.appendChild(line);
          group.appendChild(head);
        });
      });
    }

    drawField();

    let currentLvl = 1;
    function setRadius(lvl) {
      currentLvl = lvl;
      
      // Update buttons
      document.querySelectorAll('.btn-step').forEach((b, i) => {
        b.classList.toggle('active', i + 1 === lvl);
      });

      // Update ring highlights
      for (let i = 1; i <= 3; i++) {
        const ring = document.getElementById(`ring${i}`);
        if (ring) ring.classList.toggle('active', i === lvl);
      }

      // Dim/highlight arrows
      for (let i = 1; i <= 3; i++) {
        const els = document.querySelectorAll(`.arrow-lvl-${i}`);
        els.forEach(el => {
          if (i === lvl) {
            el.classList.remove('dimmed');
          } else {
            el.classList.add('dimmed');
          }
        });
      }

      // Update readout text
      const readout = document.getElementById('strengthText');
      if (lvl === 1) readout.textContent = 'g = 1 g₀ (100%)';
      if (lvl === 2) readout.textContent = 'g = ¼ g₀ (25%)';
      if (lvl === 3) readout.textContent = 'g = ⅑ g₀ (11%)';
    }

    // Initialize with level 1 focus
    setRadius(1);
  </script>
</body>
</html>

Gravitational Field Strength and Newton's Law of Gravitation

<!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="16:10">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    body {
      width: 100%;
      height: 100%;
      background: #ffffff;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 8px;
      user-select: none;
    }
    .svg-container {
      width: 100%;
      max-width: 640px;
      height: auto;
      display: flex;
      justify-content: center;
      align-items: center;
    }
    svg {
      width: 100%;
      height: auto;
      overflow: visible;
    }
    .panel-box {
      cursor: pointer;
      transition: opacity 0.2s ease;
    }
    .panel-box:hover {
      opacity: 0.95;
    }
  </style>
</head>
<body>
  <div class="svg-container">
    <svg viewBox="0 0 640 390" xmlns="http://www.w3.org/2000/svg">
      <defs>
        
        <marker id="arrow-green" viewBox="0 0 10 10" refX="5" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1.5 L 10 5 L 0 8.5 z" fill="#16a34a"/>
        </marker>
        <marker id="arrow-red" viewBox="0 0 10 10" refX="5" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1.5 L 10 5 L 0 8.5 z" fill="#dc2626"/>
        </marker>
        <marker id="arrow-blue" viewBox="0 0 10 10" refX="5" refY="5" markerWidth="5" markerHeight="5" orient="auto-start-reverse">
          <path d="M 0 1.5 L 10 5 L 0 8.5 z" fill="#2563eb"/>
        </marker>
        <marker id="arrow-amber" viewBox="0 0 10 10" refX="5" refY="5" markerWidth="5" markerHeight="5" orient="auto-start-reverse">
          <path d="M 0 1.5 L 10 5 L 0 8.5 z" fill="#d97706"/>
        </marker>

        
        <radialGradient id="earthGrad" cx="50%" cy="30%" r="70%">
          <stop offset="0%" stop-color="#60a5fa"/>
          <stop offset="60%" stop-color="#2563eb"/>
          <stop offset="100%" stop-color="#1d4ed8"/>
        </radialGradient>
        <linearGradient id="correctBg" x1="0" y1="0" x2="0" y2="1">
          <stop offset="0%" stop-color="#f0fdf4"/>
          <stop offset="100%" stop-color="#ffffff"/>
        </linearGradient>
        <linearGradient id="errorBg" x1="0" y1="0" x2="0" y2="1">
          <stop offset="0%" stop-color="#fef2f2"/>
          <stop offset="100%" stop-color="#ffffff"/>
        </linearGradient>
      </defs>

      
      <line x1="320" y1="15" x2="320" y2="375" stroke="#e2e8f0" stroke-width="2" stroke-dasharray="6,6"/>

      
      <g class="panel-box" id="correctPanel">
        
        <rect x="10" y="10" width="300" height="370" rx="12" fill="url(#correctBg)" stroke="#bbf7d0" stroke-width="1.5"/>
        
        
        <rect x="75" y="22" width="170" height="32" rx="16" fill="#dcfce7" stroke="#86efac" stroke-width="1"/>
        <text x="160" y="43" text-anchor="middle" font-size="14" font-weight="700" fill="#15803d">
          ✓ CORRECT: r = R<tspan font-size="11" dy="3">E</tspan><tspan font-size="14" dy="-3"> + h</tspan>
        </text>

        
        <circle cx="160" cy="275" r="4.5" fill="#1e2945"/>
        <text x="160" y="295" text-anchor="middle" font-size="12" font-weight="600" fill="#475569">Center</text>

        
        <path d="M 60 275 A 100 100 0 0 1 260 275 Z" fill="url(#earthGrad)" stroke="#1d4ed8" stroke-width="2"/>
        <text x="160" y="240" text-anchor="middle" font-size="14" font-weight="700" fill="#ffffff" letter-spacing="1">EARTH</text>

        
        
        <rect x="126" y="80" width="22" height="12" rx="2" fill="#38bdf8" stroke="#0284c7" stroke-width="1.5"/>
        <line x1="137" y1="80" x2="137" y2="92" stroke="#0284c7" stroke-width="1"/>
        <rect x="172" y="80" width="22" height="12" rx="2" fill="#38bdf8" stroke="#0284c7" stroke-width="1.5"/>
        <line x1="183" y1="80" x2="183" y2="92" stroke="#0284c7" stroke-width="1"/>
        
        <rect x="151" y="78" width="18" height="16" rx="3" fill="#f8fafc" stroke="#475569" stroke-width="1.5"/>
        <circle cx="160" cy="86" r="3" fill="#fbbf24"/>

        
        
        <line x1="45" y1="275" x2="160" y2="275" stroke="#94a3b8" stroke-width="1" stroke-dasharray="3,3"/>
        
        <line x1="120" y1="175" x2="225" y2="175" stroke="#94a3b8" stroke-width="1" stroke-dasharray="3,3"/>
        
        <line x1="45" y1="86" x2="160" y2="86" stroke="#94a3b8" stroke-width="1" stroke-dasharray="3,3"/>

        
        <line x1="205" y1="270" x2="205" y2="180" stroke="#2563eb" stroke-width="1.75" marker-start="url(#arrow-blue)" marker-end="url(#arrow-blue)"/>
        <rect x="195" y="215" width="26" height="18" rx="4" fill="#eff6ff"/>
        <text x="208" y="229" text-anchor="middle" font-size="13" font-weight="700" fill="#1d4ed8">R<tspan font-size="10" dy="2">E</tspan></text>

        
        <line x1="205" y1="170" x2="205" y2="92" stroke="#d97706" stroke-width="1.75" marker-start="url(#arrow-amber)" marker-end="url(#arrow-amber)"/>
        <rect x="198" y="121" width="18" height="18" rx="4" fill="#fffbeb"/>
        <text x="207" y="135" text-anchor="middle" font-size="13" font-weight="700" fill="#b45309">h</text>

        
        <line x1="55" y1="270" x2="55" y2="92" stroke="#16a34a" stroke-width="2.5" marker-start="url(#arrow-green)" marker-end="url(#arrow-green)"/>
        <rect x="25" y="169" width="60" height="24" rx="6" fill="#16a34a"/>
        <text x="55" y="186" text-anchor="middle" font-size="14" font-weight="800" fill="#ffffff">r (total)</text>
      </g>


      
      <g class="panel-box" id="errorPanel">
        
        <rect x="330" y="10" width="300" height="370" rx="12" fill="url(#errorBg)" stroke="#fecaca" stroke-width="1.5"/>
        
        
        <rect x="405" y="22" width="150" height="32" rx="16" fill="#fee2e2" stroke="#fca5a5" stroke-width="1"/>
        <text x="480" y="43" text-anchor="middle" font-size="14" font-weight="700" fill="#b91c1c">
          ✗ ERROR: r = h
        </text>

        
        <circle cx="480" cy="275" r="4" fill="#cbd5e1"/>
        <line x1="474" y1="269" x2="486" y2="281" stroke="#ef4444" stroke-width="1.5"/>
        <line x1="486" y1="269" x2="474" y2="281" stroke="#ef4444" stroke-width="1.5"/>
        <text x="480" y="295" text-anchor="middle" font-size="11" font-weight="600" fill="#94a3b8">Ignored</text>

        
        <path d="M 380 275 A 100 100 0 0 1 580 275 Z" fill="url(#earthGrad)" stroke="#1d4ed8" stroke-width="2" opacity="0.6"/>
        <text x="480" y="240" text-anchor="middle" font-size="14" font-weight="700" fill="#ffffff" letter-spacing="1" opacity="0.8">EARTH</text>

        
        
        <rect x="446" y="80" width="22" height="12" rx="2" fill="#38bdf8" stroke="#0284c7" stroke-width="1.5"/>
        <line x1="457" y1="80" x2="457" y2="92" stroke="#0284c7" stroke-width="1"/>
        <rect x="492" y="80" width="22" height="12" rx="2" fill="#38bdf8" stroke="#0284c7" stroke-width="1.5"/>
        <line x1="503" y1="80" x2="503" y2="92" stroke="#0284c7" stroke-width="1"/>
        
        <rect x="471" y="78" width="18" height="16" rx="3" fill="#f8fafc" stroke="#475569" stroke-width="1.5"/>
        <circle cx="480" cy="86" r="3" fill="#fbbf24"/>

        
        <line x1="420" y1="175" x2="555" y2="175" stroke="#94a3b8" stroke-width="1" stroke-dasharray="3,3"/>
        
        <line x1="420" y1="86" x2="555" y2="86" stroke="#94a3b8" stroke-width="1" stroke-dasharray="3,3"/>

        
        <line x1="535" y1="170" x2="535" y2="92" stroke="#dc2626" stroke-width="2.5" marker-start="url(#arrow-red)" marker-end="url(#arrow-red)"/>
        <rect x="510" y="120" width="50" height="24" rx="6" fill="#dc2626"/>
        <text x="535" y="137" text-anchor="middle" font-size="13" font-weight="800" fill="#ffffff">r = h</text>

        
        <rect x="375" y="205" width="90" height="24" rx="6" fill="#fef2f2" stroke="#f87171" stroke-width="1"/>
        <text x="420" y="221" text-anchor="middle" font-size="11" font-weight="700" fill="#dc2626">Misses R<tspan font-size="9" dy="2">E</tspan> !</text>
      </g>
    </svg>
  </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">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    }

    body {
      background-color: #f8f9fa;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      padding: 12px 16px;
      min-height: 100%;
      user-select: none;
      -webkit-user-select: none;
    }

    .header-panel {
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      justify-content: center;
      gap: 10px 16px;
      width: 100%;
      max-width: 600px;
    }

    .formula-badge {
      display: inline-flex;
      align-items: center;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 6px 14px;
      font-size: 17px;
      font-weight: 700;
      letter-spacing: 0.3px;
      color: #0f172a;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
    }

    .formula-badge .frac {
      display: inline-flex;
      flex-direction: column;
      vertical-align: middle;
      text-align: center;
      padding: 0 4px;
      font-size: 15px;
      line-height: 1.1;
    }

    .formula-badge .num {
      border-bottom: 1.5px solid #1e2945;
      padding-bottom: 1px;
    }

    .formula-badge .den {
      padding-top: 1px;
    }

    .constant-badge {
      display: inline-flex;
      align-items: center;
      background: #eff6ff;
      border: 1px solid #bfdbfe;
      border-radius: 8px;
      padding: 6px 12px;
      font-size: 13px;
      font-weight: 600;
      color: #1e40af;
    }

    .constant-badge sub, .constant-badge sup {
      font-size: 10px;
    }

    .diagram-area {
      width: 100%;
      max-width: 600px;
      flex-grow: 1;
      display: flex;
      align-items: center;
      justify-content: center;
    }

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

    .control-panel {
      width: 100%;
      max-width: 500px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 12px;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px 16px;
      box-shadow: 0 1px 2px rgba(0,0,0,0.03);
    }

    .slider-label {
      font-size: 13px;
      font-weight: 600;
      color: #475569;
      white-space: nowrap;
    }

    .range-input {
      flex: 1;
      height: 6px;
      accent-color: #2563eb;
      cursor: pointer;
    }

    .force-val {
      font-size: 13px;
      font-weight: 700;
      color: #0f172a;
      min-width: 58px;
      text-align: right;
    }
  </style>
</head>
<body>

  
  <div class="header-panel">
    <div class="formula-badge">
      <span>F<sub>g</sub> = G</span>
      <span class="frac">
        <span class="num">M₁ · M₂</span>
        <span class="den">r²</span>
      </span>
    </div>
    <div class="constant-badge">
      G = 6.674 × 10<sup>−11</sup> N·m²/kg²
    </div>
  </div>

  
  <div class="diagram-area">
    <svg viewBox="0 0 600 230" id="svgStage">
      <defs>
        
        <radialGradient id="planetGrad" cx="35%" cy="35%" r="65%">
          <stop offset="0%" stop-color="#60a5fa" />
          <stop offset="60%" stop-color="#2563eb" />
          <stop offset="100%" stop-color="#1d4ed8" />
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        <radialGradient id="moonGrad" cx="35%" cy="35%" r="65%">
          <stop offset="0%" stop-color="#fb923c" />
          <stop offset="60%" stop-color="#ea580c" />
          <stop offset="100%" stop-color="#c2410c" />
        </radialGradient>

        
        <marker id="arrowRight" markerWidth="8" markerHeight="8" refX="6" refY="4" orient="auto">
          <path d="M 0 1 L 7 4 L 0 7 z" fill="#0284c7" />
        </marker>
        <marker id="arrowLeft" markerWidth="8" markerHeight="8" refX="2" refY="4" orient="auto">
          <path d="M 7 1 L 0 4 L 7 7 z" fill="#0284c7" />
        </marker>
        <marker id="distTick" markerWidth="2" markerHeight="12" refX="1" refY="6" orient="auto">
          <line x1="1" y1="0" x2="1" y2="12" stroke="#64748b" stroke-width="2" />
        </marker>
      </defs>

      
      <g id="distGroup">
        <line id="distLine" x1="130" y1="120" x2="470" y2="120" stroke="#94a3b8" stroke-width="1.5" stroke-dasharray="5 5" />
        
        <line id="dimLine" x1="130" y1="42" x2="470" y2="42" stroke="#64748b" stroke-width="1.5" marker-start="url(#distTick)" marker-end="url(#distTick)" />
        <line id="dropLeft" x1="130" y1="42" x2="130" y2="120" stroke="#cbd5e1" stroke-width="1" stroke-dasharray="3 3" />
        <line id="dropRight" x1="470" y1="42" x2="470" y2="120" stroke="#cbd5e1" stroke-width="1" stroke-dasharray="3 3" />
        <rect id="dimBox" x="235" y="28" width="130" height="26" rx="5" fill="#f8f9fa" />
        <text id="dimText" x="300" y="46" fill="#475569" font-size="13" font-weight="700" text-anchor="middle">r (center distance)</text>
      </g>

      
      <g id="body1" transform="translate(130, 120)">
        <circle r="44" fill="url(#planetGrad)" filter="drop-shadow(0 4px 6px rgba(37,99,235,0.25))" />
        <circle r="3" fill="#ffffff" />
        <text y="68" fill="#1e2945" font-size="14" font-weight="700" text-anchor="middle">Mass M₁</text>
      </g>

      
      <g id="body2" transform="translate(470, 120)">
        <circle r="30" fill="url(#moonGrad)" filter="drop-shadow(0 4px 6px rgba(234,88,12,0.25))" />
        <circle r="3" fill="#ffffff" />
        <text y="54" fill="#1e2945" font-size="14" font-weight="700" text-anchor="middle">Mass M₂</text>
      </g>

      
      
      <g id="vectorGroup1">
        <line id="vec1" x1="130" y1="120" x2="205" y2="120" stroke="#0284c7" stroke-width="4" stroke-linecap="round" marker-end="url(#arrowRight)" />
        <text id="labelF1" x="168" y="106" fill="#0284c7" font-size="15" font-weight="800" text-anchor="middle">+F</text>
      </g>

      
      <g id="vectorGroup2">
        <line id="vec2" x1="470" y1="120" x2="395" y2="120" stroke="#0284c7" stroke-width="4" stroke-linecap="round" marker-end="url(#arrowRight)" />
        <text id="labelF2" x="432" y="106" fill="#0284c7" font-size="15" font-weight="800" text-anchor="middle">−F</text>
      </g>
    </svg>
  </div>

  
  <div class="control-panel">
    <span class="slider-label">Distance (r):</span>
    <input type="range" id="distSlider" class="range-input" min="260" max="440" value="340" step="2">
    <span class="force-val" id="forceReadout">1.00 × F</span>
  </div>

  <script>
    const slider = document.getElementById('distSlider');
    const body1 = document.getElementById('body1');
    const body2 = document.getElementById('body2');
    const distLine = document.getElementById('distLine');
    const dimLine = document.getElementById('dimLine');
    const dropLeft = document.getElementById('dropLeft');
    const dropRight = document.getElementById('dropRight');
    const dimBox = document.getElementById('dimBox');
    const dimText = document.getElementById('dimText');
    const vec1 = document.getElementById('vec1');
    const vec2 = document.getElementById('vec2');
    const labelF1 = document.getElementById('labelF1');
    const labelF2 = document.getElementById('labelF2');
    const forceReadout = document.getElementById('forceReadout');

    const BASE_DIST = 340;
    const BASE_FORCE_LEN = 75;

    function updatePositions() {
      const r = parseFloat(slider.value);
      const centerX = 300;
      const x1 = centerX - r / 2;
      const x2 = centerX + r / 2;

      // Inverse-square force scaling
      const forceRatio = Math.pow(BASE_DIST / r, 2);
      const fLength = Math.min(Math.max(BASE_FORCE_LEN * forceRatio, 24), (r / 2) - 30);

      // Update Planet Positions
      body1.setAttribute('transform', `translate(${x1}, 120)`);
      body2.setAttribute('transform', `translate(${x2}, 120)`);

      // Update Distance Dimension Lines
      distLine.setAttribute('x1', x1);
      distLine.setAttribute('x2', x2);
      dimLine.setAttribute('x1', x1);
      dimLine.setAttribute('x2', x2);
      dropLeft.setAttribute('x1', x1);
      dropLeft.setAttribute('x2', x1);
      dropRight.setAttribute('x1', x2);
      dropRight.setAttribute('x2', x2);

      // Force Vector 1 (Rightwards from M1)
      vec1.setAttribute('x1', x1);
      vec1.setAttribute('x2', x1 + fLength);
      labelF1.setAttribute('x', x1 + fLength / 2);

      // Force Vector 2 (Leftwards from M2)
      vec2.setAttribute('x1', x2);
      vec2.setAttribute('x2', x2 - fLength);
      labelF2.setAttribute('x', x2 - fLength / 2);

      // Update Readout
      forceReadout.textContent = forceRatio.toFixed(2) + ' × F';
    }

    slider.addEventListener('input', updatePositions);
    updatePositions();
  </script>
</body>
</html>

Regla del octeto y estructuras de Lewis

Enlace iónico y redes cristalinas

Enlace covalente simple, múltiple y coordinado

Polaridad del enlace y momento dipolar

Teoría de repulsión de pares electrónicos (RPECV)

Hibridación de orbitales sp, sp2 y sp3

Enlace metálico y conductividad

Fuerzas intermoleculares: dipolo-dipolo y dispersión de London

Puentes de hidrógeno y propiedades del agua

Relación entre enlace y propiedades macroscópicas

science

Enlace químico y geometría molecular

Concepto de fuerza y primera ley de Newton

Diagramas de cuerpo libre en una y dos dimensiones

Segunda ley de Newton: fuerza, masa y aceleración

Tercera ley de Newton: pares de acción y reacción

Masa, peso y fuerza de gravedad local

Fuerza normal y fuerza de tensión

Fuerza de fricción estática y cinética

Leyes de Newton y fuerzas fundamentales

Vectores, sistemas de referencia y posición

Desplazamiento, distancia, velocidad y rapidez

Movimiento rectilíneo uniforme (MRU)

Aceleración media e instantánea

Movimiento rectilíneo uniformemente acelerado (MRUA)

Análisis gráfico del movimiento en una dimensión

Caída libre y lanzamiento vertical

Movimiento de proyectiles y tiro parabólico

Alcance máximo y tiempo de vuelo en proyectiles

Movimiento circular uniforme (MCU)

Aceleración centrípeta y movimiento circular variado

Cinemática y movimiento en una y dos dimensiones

Gravitational Potential Energy and Orbital Velocities

Coulomb's Law and Electric Field Strength Calculations

Electric Potential, Equipotential Surfaces, and Work Done

Magnetic Force on Moving Charges and Current-Carrying Wires

Magnetic Flux Linkage and Faraday's Law of Induction

Faraday's Law and Lenz's Law of Electromagnetic Induction

Gravitational, Electrostatic, and Magnetic Fields

Tercera ley de Newton: acción y reacción

Diagramas de cuerpo libre

Dinámica en planos inclinados

Sistemas de cuerpos conectados y poleas

Fuerza centrípeta y dinámica circular

Fuerza elástica y ley de Hooke

Torque y equilibrio estático rotacional

Dinámica y leyes de Newton

Cantidad de movimiento lineal e impulso

Conservación de la cantidad de movimiento

Colisiones elásticas e inelásticas en una dimensión

Colisiones en dos dimensiones

Seguridad vial y física de los impactos

Cantidad de movimiento y colisiones

Ley de gravitación universal de Newton

Campo gravitacional y leyes de Kepler

Carga eléctrica y formas de electrización

Ley de Coulomb y fuerza electrostática

Campo eléctrico y líneas de fuerza

Potencial eléctrico y diferencia de potencial

 Campos y fuerzas: gravitación y electrostática

Corriente eléctrica y resistencia: ley de Ohm

Circuitos en serie y en paralelo

Circuitos mixtos y leyes de Kirchhoff

Potencia eléctrica y efecto Joule

Capacitancia y almacenamiento de energía

Seguridad eléctrica e instalaciones domiciliarias

Circuitos eléctricos de corriente directa

Modelos cosmológicos: de los epiciclos al heliocentrismo

Balanza de torsión de Cavendish y medición de la constante G

Concepto de campo gravitacional e intensidad g

Variación de la gravedad con la altitud, profundidad y latitud

Líneas de campo y superficies equipotenciales gravitacionales

Gravitación universal y campo gravitatorio

Campo magnético e imanes permanentes

Fuerza magnética sobre cargas en movimiento

Campos magnéticos generados por corrientes

Inducción electromagnética: ley de Faraday y Lenz

Motores, generadores y transformadores

Electromagnetismo

Energía potencial gravitacional a escala planetaria

Velocidad de escape y pozos de potencial gravitatorio

Dinámica de satélites artificiales en órbita circular

Fuerzas de marea e interacción gravitacional Tierra-Luna

Maniobras espaciales y transferencia orbital de Hohmann

Agujeros negros, radio de Schwarzschild y relatividad

Analogías estructurales entre campos gravitatorios y electrostáticos

Mecánica celeste y dinámica orbital

Carga eléctrica: conservación y cuantización

Métodos de electrización: fricción, contacto e inducción

Conductores, aislantes y polarización dieléctrica

Superposición vectorial de fuerzas electrostáticas

Origen electrostático de las fuerzas de contacto macroscópicas

Carga eléctrica y fuerzas electrostáticas

Campo eléctrico de distribuciones discretas de carga

Dipolo eléctrico y momento dipolar en campos uniformes

Flujo eléctrico y ley de Gauss conceptual

Conductores en equilibrio electrostático y blindaje

Campo eléctrico: distribuciones, ley de Gauss y conductores

Movimiento de partículas cargadas en campos eléctricos uniformes

Generador de Van de Graaff y ruptura dieléctrica del aire

Comparación cuantitativa entre campos gravitacionales y electrostáticos

Aplicaciones tecnológicas: fotocopiadoras, filtros y pintura

Fenómenos y aplicaciones electrostáticas

Energía potencial electrostática en sistemas de cargas

Superficies equipotenciales y relación con el campo eléctrico

Asociación de condensadores en serie y en paralelo

Potencial eléctrico y capacitancia

The Concept of a Force Field in Physics

Representing Force Fields with Field Lines

Newton's Law of Universal Gravitation

Gravitational Field Strength: g = F/m

Gravitational Potential: Vg = -GM/r

Gravitational Potential Energy and Work Done in Fields

Equipotential Surfaces and Field Gradient: g = -dV/dr

Orbital Mechanics and Satellite Motion

Geostationary and Low Earth Polar Orbits

Escape Velocity from Gravitational Wells

A-Level Physics: Gravitational Fields and Orbital Mechanics

Coulomb's Law for Electrostatic Force

Defining Electric Field as Force per Unit Charge

Uniform Electric Fields Between Parallel Plates: E = V/d

Electric Potential: V = Q / (4πε0 r)

Comparing Gravitational and Electrostatic Fields

Motion of Charged Particles in Uniform Electric Fields

Millikan's Oil Drop Experiment and Charge Quantisation

A-Level Physics: Electric Fields and Potential

Magnetic Flux Density and Field Patterns

Magnetic Force on a Current-Carrying Conductor: F = BIl sin θ

Magnetic Fields Act on Moving Charges

Circular Motion of Charged Particles in Magnetic Fields

The Cyclotron Particle Accelerator

Velocity Selectors and Mass Spectrometers

The Hall Effect and Measuring Magnetic Fields

A-Level Physics: Magnetic Fields and Moving Charges

Espectrometría de masas y aceleradores ciclotrón

Fuerza magnética sobre conductores con corriente: ley de Laplace

Torque sobre espiras y principio del motor eléctrico

Ley de Ampère y campo magnético en solenoides y toroides

Fuerza magnética entre conductores paralelos y definición del amperio

Campos magnéticos y fuerzas magnéticas

Magnetic Flux and Flux Linkage: Φ = BA and NΦ

EMF Induced in Moving Conductors and Rotating Coils

Alternating Current Generators and Transformers

Eddy Currents and Energy Losses in Electromagnetism

Synchrotrons and Modern Particle Colliders

Unification of Forces and Gravitational Waves

Synoptic Problems in Gravitational, Electric and Magnetic Fields

A-Level Physics: Electromagnetic Induction and Applications

Flujo magnético y ley de inducción de Faraday

Ley de Lenz y corrientes de Foucault (Eddy)

Generadores eléctricos y transformadores de voltaje

Autoinducción, inductores y energía del campo magnético

Ecuaciones de Maxwell y síntesis electromagnética

Espectro electromagnético y naturaleza de la luz

Campos de fuerza fundamentales: gravedad y electromagnetismo

Inducción electromagnética y síntesis de Maxwell

Concept and Definition of Gravitational Field Strength

Newton's Law of Gravitation for Point and Spherical Masses

Radial Gravitational Field Strength and the Inverse Square Law

Gravitational Potential: Definition, Zero Reference, and Sign Convention

Calculating Gravitational Potential: V = -GM/r

Gravitational Potential Energy and Work Done Moving Masses

Relating Field Strength to Potential Gradient: g = -dV/dr

Equipotential Surfaces and Field Lines in Radial and Uniform Fields

A-Level Physics: Gravitational Field Strength and Potential

Orbital Speeds and Deriving Kepler's Third Law: T² ∝ r³

Geostationary, Polar, and Low Earth Satellite Orbits

Escape Velocity: Derivation and Energetics

Mass vs Charge as Sources of Force

Comparing Electric and Gravitational Fields

A-Level Physics: Orbital Mechanics and Field Comparisons

Ondas mecánicas: propagación longitudinal y transversal

Acústica: velocidad del sonido, intensidad y decibelios

Ondas estacionarias y resonancia en cuerdas y columnas de aire

Efecto Doppler en ondas acústicas y electromagnéticas

Fenómenos ondulatorios: reflexión, refracción, difracción e interferencia

Ondas mecánicas y acústica

What is a Test Charge?

Coulomb's Law and Permittivity of Free Space: F = Q1 Q2 / (4πε0 r²)

Electric Field Calculations for Point Charges

Vector Superposition of Electric Fields from Multiple Charges

Constant Electric Field Between Parallel Plates

Trajectory and Kinematics of Charged Particles in Uniform Electric Fields

A-Level Physics: Electric Fields, Forces, and Particle Kinematics

Electric Potential: Energy per Unit Charge

Calculating Electric Potential from a Point Charge

Calculating Electric Potential Energy Between Two Charges

Work Done Moving a Charge Between Potentials

Relating Electric Field to Potential Difference

Millikan's Oil Drop Experiment and Quantisation of Electric Charge

A-Level Physics: Electric Potential, Energy, and Charge Quantisation

Magnetic Flux Density (B-Fields) and the Tesla

Magnetic Fields Act on Electric Currents

Calculating Force on a Straight Conductor: F = BIl sin θ

Measuring Magnetic Flux Density with a Current Balance

Calculating Magnetic Force on Moving Charges

Circular Trajectories of Charged Particles in Uniform B-Fields

OGS.13.PS.9

Aligned learning resources

Related diagrams