Question

You choose to use video analysis to get the jump height of volleyball players in actual game conditions. After doing a stopwatch analysis you found out that the playback device resolution is 30 pictures per second. For one athlete by counting picture you find that they were in the air for 34 pictures. How long did it take to reach the peak?

Answer 1

You have found that the playback device resolution is 30 pictures per second. Therefore, 30 pictures are taken in 1 second.

This tells us that since you took 34 pictures of the athlete in the air, the time in which the athlete was in the air was

For any object that jumps up and then comes down, if we neglect air resistance, then the time to reach the peak starting from the ground is equal to the time to come back to the ground. In both cases, the time is given by where h is the maximum height it reaches and g is the acceleration due to gravity. So,

The total time it spends in the air is given by the sum of the time it takes to reach the peak and the time it takes to come back.

From the two above relations, we get, . Therefore, since t_{air}=1.133s, we get t_{up}=0.567s

The time the athlete took to reach the peak is 0.567s