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

Answer:

$Velocity = 0.5625m/s$

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

$\frac{45}{80} = \frac{80v}{80}$

$0.5625 = v$

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