Question

Ques

A skateboarder is cruising on his skateboard at 3 m/s and has a total mass of 70 kg. A friend jumps on
(from standing still). What is the new velocity of the skateboarder if the friend has a mass of 50 kg?

Answer 1

When a particle or a system of particles move in a system where no external force acts, then the total linear momentum of the particle system remains constant.

Step-by-step explanation:

Given data:

Total mass of the skateboarder,
`m_(1) = 70 \ kg`

Mass of the friend,
`m_(2) = 50 \ kg`

Initial velocity of the skateboarder,
`u_(1) = 3 \ m/s`

Initial velocity of the the friend,
`u_(2) = 0`

Let the new velocity of the skateboarder when his friend jumps be
`v`.

From the conservation law of linear momentum,

`m_(1)u_(1) + m_(2)u_(2) = (m_(1) + m_(2))v`

`70 * 3 + 50 * 0 = (70 + 50)v`

`\Rightarrow \ v &= 1.75 \ m/s.`