Question

April sits at rest on a skateboard. She has a mass of 65 kg. Her friend throws

her a suitcase (m= 15 kg) at a speed of 3 m/s. If she catches it, how fast will
she, the skateboard, and the suitcase move?

Answer 1

`Velocity = 0.5625m/s`

Step-by-step explanation:

Given

Represent mass of April with M and mass of the suitcase with m; such that

`M = 65kg`

`m = 15kg`

Represent initial velocity of April with U and initial velocity of the suitcase with u; such that

`U = 0m/s` (because she's resting on the skateboard, initially)

`u = 3m/s`

After she catches the suitcase, she, the skateboard and the suitcase moves at the same velocity.

Represent this velocity with v

The above given information can be representing using law of conservation of momentum.

`MU + mu = (M + m)v`

Substitute the values of M,U, m and u.

This gives

`65 * 0 + 15 * 3 = (65 + 15)v`

`0 + 45 = (80)v`

`45 = 80v`

Divide both sides by 80

`(45)/(80) = (80v)/(80)`

`0.5625 = v`

Hence, they moved at a velocity of 0.5625m/s