Question

Jack stands at rest on a skateboard. The mass of Jack and the skateboard together is 75 kg. Ryan throws a 3.0 kg ball horizontally to the right at 4.0 m/s to Jack, who catches it. What is the initial momentum of the system in kg m/s?

Answer 1

The initial momentum of the system is 12 kg m/s

Step-by-step explanation:

Hi there!

The momentum of the system is calculated as the sum of the momenta of the objects that compose the system, in this case, Jack and the ball.

The momentum of each object is calculated as follows:

p = m · v

Where:

p = momentum

m = mass

v = velocity

The initial momentum of the system is the momentum before Jack catches the ball and is given by the sum of the momentum of the ball (pb) plus the momentum of Jack (pj) (let´s consider the right direction as positive):

Initial momentum = pb + pj

initial momentum = mb · vb + mj · vj

initial momentum = 3.0 kg · 4.0 m/s + 75 kg · 0 m/s

initial momentum = 12 kg m/s

The initial momentum of the system is 12 kg m/s