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?
The ball never went faster than 3 m/s.
At a certain point, the ball traveled faster than 3 m/s.
It took the ball 3 s to reach the halfway point down the ramp.
The ball traveled at a constant speed of 3 m/s.

Answer 1

Only: "At a certain point, the ball traveled faster than 3 m/s."

Reason: average speed = total distance / total time = 3 m / t = 3 m/s so t = 1 s. If the ball never exceeded 3 m/s then its speed would be ≤3 m/s for the whole second, so its average could be at most 3 m/s, and would equal 3 m/s only if its speed were exactly 3 m/s the whole time — but it was released (started at 0), so it couldn't have been 3 m/s immediately. Therefore it must have been faster than 3 m/s at some point.

The other statements need not be true (the ball could exceed 3 m/s, need not be constant, and it certainly did not take 3 s to reach halfway).