Question

A student drops a ball from a height of 60 meters. The table below shows the ball’s speed and height as time passes.

Time (s):
0.0
0.5
1.0
1.5
2.0
2.5

Speed (m/s):
0
7
10
15
20
0

Height (m):
60
53
43
28
8
0


At what point in time does the ball have the highest kinetic energy?


A). At the start (0 seconds)

B). After 0.5 seconds

C). After 2 seconds

D). After 2.5 seconds

Answer 1

To determine the point in time at which the ball has the highest kinetic energy, we first recall that kinetic energy (KE) is given by the formula:

\[ KE = \frac{1}{2} m v^2 \]

where \( m \) is the mass of the object and \( v \) is its speed. Since the mass of the ball remains constant and does not change with time, we can focus on the speed (velocity) to determine the point of maximum kinetic energy.

Next, let's analyze the speed at each given time:

- At 0.0 seconds: Speed = 0 m/s
- At 0.5 seconds: Speed = 7 m/s
- At 1.0 seconds: Speed = 10 m/s
- At 1.5 seconds: Speed = 15 m/s
- At 2.0 seconds: Speed = 20 m/s
- At 2.5 seconds: Speed = 0 m/s

The ball's speed is highest at 2.0 seconds when the speed is 20 m/s. This means that the kinetic energy will also be highest at this moment, as kinetic energy is proportional to the square of the speed.

Thus, the answer to the question is:

**C). After 2 seconds**