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

Answer:

Final velocity will be -5.33 m/sec

Explanation:

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

Initial speed = 7.75 m/sec

Backward force $F=1.85\times 10^4N$

Time is given as $t=7.5\times 10^{-2}sec$

Impulse is given by impulse = force × time

So impulse $=-1.85\times 10^4\times 7.5\times 10^{-2}=-1387.5N-s$ ( as force is backward )

We know that impulse is given by change in momentum

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

$106\times (v_f-7.75)=-1387.5$

$v_f=-5.33m/sec$