Question

Jeb is the local tennis pro at the country club, and he needs to know at what height the tennis ball needs to be when he hits it so he can clear a 0.3 meter net from 20 meters away, and have the ball land 4 meters on the other side. Find the height at which Jeb needs to hit the ball.

Answer 1

Answer:

The height from ground, at which Jeb needs to hit the ball is 7.8 meters

Step-by-step explanation:

The given parameters are;

The distance away the tennis ball is hit = 20 meters;

The height of the tennis net = 0.3 m

The distance from the net the ball lands = 4 meters

The time the ball takes to land from the 0.3 m net height is given as follows;

t = √(h/(1/2×g)) = √(0.3/(1/2 × 9.8)) ≈ 0.2474

t ≈ 0.2474 seconds

The speed of the ball = Distance/Time = 4/0.2474 ≈ 16.166

The speed of the ball ≈ 16.166 m/s

The time it takes the ball to reach the net = 20/16.166 ≈ 1.24

The time it takes the ball to reach the net, tₓ ≈ 1.24 seconds

The height, hₓ the ball falls in 1.24 seconds is given as follows;

hₓ = 1/2·g·tₓ² = 1/2 × 9.8 × 1.24² = 7.5

The height, hₓ the ball falls in 1.24 seconds = 7.5 m

The height the ball falls in the time taken to reach the net from 20 meters = The height, hₓ the ball falls in 1.24 seconds

Therefore, the height at which Jeb needs to hit the ball = The height the ball falls in the time taken to reach the net from 20 meters + The height of the net = 7.5 m + 0.3 m = 7.8 m

The height at which Jeb needs to hit the ball = 7.8 m