Magnitude of Momentum, relative to the center of mass

[gap0063]

Homework Statement

A 4.39 g particle is moving at 4.15 m/s toward a stationary 9.64 g particle.

(a)With what speed does the heavier particle approach the center of mass of the two particles?
Answer in units of m/s.

(b) What is the magnitude of the momentum of the lighter particle, relative to the center of mass?
Answer in units of Ns.

Homework Equations

m₁v₁+m₂v₂/m₁+m₂

and

P=mv

The Attempt at a Solution

I got part (a) by using m₁v₁+m₂v₂/m₁+m₂
where v₂ is zero

so I got 1.29854 m/s which is right (this is a online homework assignment)

for part (b) I thought it was the mass of m₁= 4.39 g= 0.00439 kg

and I times it by the speed I found from part (a) but the number I'm getting isn't right (0.006402 Ns)

so what am I doing wrong?

 

[ehild]

You found the speed of the centre of mass with respect to the ground. Calculate the velocity of the lighter particle with respect to the centre of mass.

ehild

 

[gap0063]

You found the speed of the centre of mass with respect to the ground. Calculate the velocity of the lighter particle with respect to the centre of mass.

ehild

oh yes, thanks!