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M1 moments Help

2 small balls A and B have masses 0.6kg and 0.2kg respectively. They are moving towards each other in opposite directions on a horizontal table when they collide directly. Immediately before the collision, the speed of A=4.5ms and the speed of B=3ms. Immediately after the collision, A and B move in the same direction and the speed of B is twice the speed of A.
By modelling the balls as particles, find

a) the speed of B immediately after the collision

I have found this: 4.2ms^-1

b) the magnitude of the impulse exerted on B in the collision

I have found this: 1.44kgms^-1

c) The table is rough. After the collision, B moves a distance of 2m on the table before coming to rest
Find the coefficient of friction between B and the table

Here I get stuck
what i have done so far is

I know F= uR

R=mg
R=0.6g

to find F I need to use
F=ma
then I found a
by using v^2 =u^2+2as
a=-1.05
F= 0.6 X -1.05
=-0.63

then I put F and R-value to find the coefficient of friction but that is the wrong answer.Where I get wrong ????
Reply 1
Avatar for Pangol
Pangol
15
Original post by Qer
Where I get wrong ????

Momentum, not moments!

Is it because you've used the mass of A instead of B? I haven't checked all of your working, but it looks like you're doing the right things.

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