AP Physics Free Fall Questions: Prepare for Your Exam

📚 Quick Study Guide

• 🍎 Definition: Free fall is the motion of an object where the only force acting upon it is gravity. Air resistance is negligible.
• 🌍 Acceleration: The acceleration due to gravity, denoted as $g$, is approximately $9.8 m/s^2$ near the Earth's surface. Its direction is always downwards.
• 📐 Key Equations:
  • 📏 Vertical displacement: $\Delta y = v_0t + \frac{1}{2}gt^2$
  • ⏱️ Final velocity: $v = v_0 + gt$
  • 💡 Velocity-displacement relation: $v^2 = v_0^2 + 2g\Delta y$
• 📝 Important Notes:
  • 📍 Initial velocity ($v_0$) can be positive (upwards), negative (downwards), or zero.
  • ➕ When choosing a coordinate system, be consistent with the signs of displacement, velocity, and acceleration. Upwards is usually positive, downwards is negative.
  • 💨 Neglecting air resistance simplifies the problem, but remember that in real-world scenarios, it plays a significant role.

🧪 Practice Quiz

1. A ball is dropped from a height of 45 meters. How long does it take to reach the ground, assuming no air resistance?
   1. 2.14 s
   2. 3.03 s
   3. 4.29 s
   4. 9.80 s
2. An object is thrown vertically upwards with an initial velocity of 15 m/s. What is the maximum height it reaches?
   1. 11.5 m
   2. 22.9 m
   3. 34.4 m
   4. 45.8 m
3. A stone is dropped from a bridge. It hits the water 2.5 seconds later. What is the height of the bridge above the water?
   1. 12.3 m
   2. 24.5 m
   3. 30.6 m
   4. 36.8 m
4. A ball is thrown upwards with a velocity of 20 m/s. What is its velocity at the highest point?
   1. 20 m/s
   2. 9.8 m/s
   3. 4.9 m/s
   4. 0 m/s
5. An object falls from a height of 100 meters. What is its velocity just before hitting the ground?
   1. 31.3 m/s
   2. 44.3 m/s
   3. 14 m/s
   4. 9.8 m/s
6. A rock is thrown downwards with an initial speed of 5 m/s from a height of 30 m. How long does it take to reach the ground?
   1. 1.96 s
   2. 2.04 s
   3. 2.69 s
   4. 3.01 s
7. A projectile is launched vertically upward. If the time to reach its maximum height is 3 seconds, what was its initial velocity?
   1. 9.8 m/s
   2. 19.6 m/s
   3. 29.4 m/s
   4. 39.2 m/s