# Father in need of help

1. Jan 6, 2009

### Sgt

1. The problem statement, all variables and given/known data
I don't know how to use this forum so here we go. My 16 year old autisitc son is stumped with this question. If anyone can help me send him in the right direction it would be great, I am lost.

dog with a mass of 113 g runs to the right at 2.00 m/s, sees a mouse stopes using paws, slides 80.0 cm during deceleration, dog turns and runs other direction, calculate the magnitudes of change in dog's momentum AND the average frictional force that brings about this change.

He can't figure out what formula to use and I have no idea, can anyone point me in the right direction?

what happened to 2+2=4?

2. Relevant equations

3. The attempt at a solution

total 1^p=0
slow down segment = 0.226ns
run in opposite direction segment = 0.226ns

help?

2. Jan 6, 2009

Magnitude of the change in the dog's momentum basically means an Impulse. Which can be figured out using the formula J=FΔt.

J=Impulse aka the answer to the first question
F=force
Δt= Change in time

You have Δt but still need force.

F=ma

m=mass
a=acceleration

You have mass but still need acceleration

a=Δv/t

Δv=change in velocity
t=time

Hopefully you can work that out good luck and I will still be online for more question