Question

A 72-kg father who is ice skating west collides with his 28-kg son who is ice skating north. Immediately after the collision, the father and son are observed to be moving together with a velocity of 2.5 m/s, in a direction 18 degrees north of west. What were the speeds of the father and the son before the collision? ( Be sure to give both speeds)

Answer 1

Here,

let the speed of son was us

speed of father was uf

for the inital speed

we will use conservation of momentum in west and north direction

for the conservation of momentum in west direction

72 * uf = (72 + 28) * 2.5 * cos(18)

solving for uf

uf = 3.3 m/s

the initial speed of father was 3.3 m/s

for the son

using the conservation of speed in north direction

28 * us = (72 + 28) * 2.5 * sin(18)

solving us

us = 2.76 m/s

the speed of son initially was 2.76 m/s