AP Physics 1 Question 344: Answer and Explanation
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2. Which of the following correctly describes the motion of a real object in free fall? Assume that the object experiences drag force proportional to speed and that it strikes the ground before reaching terminal speed.
- A. It will fall with increasing speed and increasing acceleration.
- B. It will fall with increasing speed and decreasing acceleration.
- C. It will fall with decreasing speed and increasing acceleration.
- D. It will fall with decreasing speed and decreasing acceleration.
Correct Answer: B
An object's terminal speed is the highest speed it can reach in free fall. If it has not yet reached that speed, its speed must still be increasing. This eliminates (C) and (D). The problem says that the object will experience a drag force that increases as speed increases. Therefore, the opposing force will increase over time, which means the net force will decrease (since the force from gravity will be constant). If net force decreases, so will acceleration.