How long does it take a 9.0 N force to stop a dog and skateboard?

[Jonathan Teas]

Homework Statement

A 24.0kg dog running at a speed of 3.0m/s jumps onto a stationary skateboard that has a mass of 3.6 kg how long will it take a force with a magnitude of 9.0 N to stop the skateboard and the dog?

Homework Equations

F(change in time)=Pf-Pi
P=MV

The Attempt at a Solution

I don't understand how to calculate the length of time that it takes for the 9.0N force is going to slow down the skateboard and the dog.

 

[Delphi51]

You can use the formula you wrote: F(change in time)=Pf-Pi
Put in the numbers for the force and momentum and then you can calculate the change in time.