Question

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 0.250 m. (a) How long does the collision last? (b) What is his deceleration?

Answer 1

a) 0.067 seconds

b) 112.5 m/s²

Step-by-step explanation:

t = Time taken

u = Initial velocity = 7.5 m/s

v = Final velocity = 0

s = Displacement = 0.25 m

a = Acceleration

Eqaution of motion

`v^2-u^2=2as\\\Rightarrow a=(v^2-u^2)/(2s)\\\Rightarrow a=(0^2-7.5^2)/(2* 0.25)\\\Rightarrow a=-112.5\ m/s^2`

b) The deceleration of the football player is 112.5 m/s²

`v=u+at\\\Rightarrow t=(v-u)/(a)\\\Rightarrow t=(0-7.5)/(-112.5)\\\Rightarrow t=0.067\ s`

a) The collision lasts for 0.067 seconds