AP Physics 1 Questions on Apparent Weight and Normal Force

📚 Quick Study Guide

• ⚖️ Apparent Weight: The force experienced by an object due to contact forces, often the normal force. It's what a scale reads.
• 🍎 Normal Force ($N$): The force exerted by a surface on an object, perpendicular to the surface.
• 🤸 Equilibrium: When the net force is zero ($\sum F = 0$), acceleration is zero ($a = 0$).
• 🎢 Non-Equilibrium: When there is a net force, Newton's Second Law applies ($\sum F = ma$). The apparent weight will differ from the actual weight.
• 📐 Weight ($\mathbf{W}$): The force of gravity on an object, calculated as $W = mg$, where $m$ is mass and $g$ is the acceleration due to gravity (approximately $9.8 m/s^2$).
• ⬆️ Elevators: In an elevator accelerating upwards, the apparent weight is greater than the actual weight. In an elevator accelerating downwards, the apparent weight is less than the actual weight.

🧪 Practice Quiz

1. A person stands on a scale in an elevator. Under which condition will the scale read a value greater than the person's actual weight?
   1. The elevator is stationary.
   2. The elevator is moving upward at a constant velocity.
   3. The elevator is accelerating downward.
   4. The elevator is accelerating upward.
2. A box with a weight of 50 N rests on a horizontal surface. What is the magnitude of the normal force acting on the box?
   1. 0 N
   2. 25 N
   3. 50 N
   4. 100 N
3. A 70 kg person is in an elevator accelerating downwards at 2 m/s². What is their apparent weight?
   1. 700 N
   2. 560 N
   3. 840 N
   4. 140 N
4. A book is resting on an inclined plane. At what angle will the normal force be equal to zero?
   1. 0 degrees
   2. 45 degrees
   3. 90 degrees
   4. Never
5. Two boxes are stacked on top of each other. Box A is on top of Box B. Which statement is true about the normal force on Box B?
   1. The normal force on Box B is equal to the weight of Box A.
   2. The normal force on Box B is equal to the weight of Box B.
   3. The normal force on Box B is equal to the sum of the weights of Box A and Box B.
   4. The normal force on Box B is equal to the difference between the weights of Box A and Box B.
6. A person is standing on a scale in an elevator moving at a constant velocity. What does the scale read?
   1. A value greater than their weight.
   2. A value less than their weight.
   3. Their actual weight.
   4. Zero.
7. A block is pushed against a wall with a force $F$. The normal force on the block is:
   1. Equal to the weight of the block.
   2. Equal to the applied force $F$.
   3. Zero.
   4. Dependent on the coefficient of friction.