Question

An unwary football player collides head-on with a padded goalpost while running at 7.9 m/s and comes to a full stop after compressing the padding and his body by 0.32 m. Take the direction of the player's initial velocity as positive.

Answer 1

Acceleration, a =
`97.52 m/s^(2)`

t = 0.08 s

Solution:

As per the question:

The velocity of the player, v = 7.9 m/s

distance, d = 0.32 m

Now, consider the direction of the initial velocity of the player as positive and the acceleration to be constant:

Also, the final velocity of the player, v' = 0 m/s as he finally stops

Using the third eqn of motion:

`v'^(2) = v^(2) - 2ad`

`0 = 7.9^(2) - 2a* 0.32`

a =
`97.52 m/s^(2)`

Also, From eqn (1) of motion:

v' = v - at

0 = 7.9 - 97.52t

t = 0.08 s