Question

In a science experiment, a student releases a ball down a 3 m ramp. If the ball has an average speed of 3 m/s, which of the following must be true?
1. The ball never went faster than 3 m/s.
2. At a certain point, the ball traveled faster than 3 m/s.
3. It took the ball 3 s to reach the halfway point down the ramp.
4. The ball traveled at a constant speed of 3 m/s.

Answer 1

None of them must be true.

Reasoning:
- Average speed = total distance / total time = 3 m / t = 3 m/s ⇒ t = 1 s for the whole ramp.
- 1. Not required. If the ball starts from rest and accelerates uniformly to 6 m/s, the average over 1 s is 3 m/s, so it did go faster than 3 m/s.
- 2. Not required. If the ball moved at constant 3 m/s, it never exceeded 3 m/s.
- 3. False. Half the distance is 1.5 m; total time is 1 s, so it cannot take 3 s to reach halfway.
- 4. Not required. Average 3 m/s can come from constant motion or from varying speeds (e.g., accelerating), so constant speed is not guaranteed.