An unwary football player collides with a padded goalpost while running at a velocity of 7.50 m/s and comes to a full stop after compressing the padding and his body 0.350 m. (a) What is his deceleration? (b) How long does the collision last?

(a) the deceleration of the player is - 80.36 m/s²

(b) the time the collision last is 0.093 s

Explanation:

Given;

Initial velocity of the football player, u = 7.50 m/s

Final velocity of the football player, v = 0

distance traveled = compression of the pad, s = 0.35 m

Part (a) the deceleration of the player

v² = u² + 2as

0 = 7.5² + (2 x 0.35) a

0 = 56.25 + 0.7a

- 56.25 = 0.7a

a = - 56.25 / 0.7

a = - 80.36 m/s²

Part (b) the time the collision last

v = u + at

t = (v - u) / a

t = (0 - 7.5) / - 80.36

t = - 7.5 / - 80.36

t = 0.093 s