Question

Calculate the final speed (in m/s) of a 114 kg rugby player who is initially running at 7.25 m/s but collides head-on with a padded goalpost and experiences a backward force of 1.75 ✕ 104 N for 6.50 ✕ 10−2 s.

Answer 1

Impulse exerted by a force f for time t is given by the change in momentum i.e.,

m is the mass of the object and u, v are the initial and final velocities.

The player experiences a backward force.

If the rugby player is moving along +X axis with a speed of u=7.25 m/s he must bounce back with another velocity v in the -X axis

Putting the values,

The minus sign does confirm the fact that the player bounces in the backward direction and with avelocity 2.73 m/s