Question

A football player kicks a football straight up in the air. The velocity of the ball right after he hits it is 20 ms−1. It flies in the air for 2 seconds before it reaches its peak. What is the height reached by the ball before it starts coming down?
1 40 m
2 200 m
3 20 m
4 210 m

Answer 1

Answer:

3. 20m

Explanation:

Given:

Initial velocity (u) = 20 m/s

Time (t) = 2 seconds

Deceleration (negative acceleration) = g = -9.8 m/s²

To find:

Displacement (s)

Method to find:

s = ut + 1/2at² (2nd formula of motion)

⇒ s = (20*2) + (1/2 * -9.8 * 2 * 2)

⇒ s = 40 + (-19.6)

⇒ s = 20.4 m ≈ 20 m

Hence, the ball reaches a height of roughly 20 m before it starts coming down.