Question

Calculate the final speed (in m/s) of a 106 kg rugby player who is initially running at 7.75 m/s but collides head-on with a padded goalpost and experiences a backward force of 1.85 ✕ 10⁴ N for 7.50 ✕ 10⁻²s.

Answer 1

Final velocity will be -5.33 m/sec

Step-by-step explanation:

We have given mass of the rugby player m = 106 kg

Initial speed = 7.75 m/sec

Backward force
`F=1.85* 10^4N`

Time is given as
`t=7.5* 10^(-2)sec`

Impulse is given by impulse = force × time

So impulse
`=-1.85* 10^4* 7.5* 10^(-2)=-1387.5N-s` ( as force is backward )

We know that impulse is given by change in momentum

So
`m(v_f-v_i)=-1387.5`

`106* (v_f-7.75)=-1387.5`

`v_f=-5.33m/sec`