# Center of mass and velocity problem

If a particle of mass 5.30 kg is moving east at 10.0 m/s and a particle of mass 18.0 kg is moving west at 10.0 m/s, what is the velocity of the center of mass of the pair?

I used the equation
Vcm = P/M
Vcm = [(5.70)(10) + (15)(10)] / [(5.70)+(15)]
Vcm = 10 ms

however, it says that is not the correct answer.
I don't understand why. can someone help?
thanks

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kbyws37 said:
If a particle of mass 5.30 kg is moving east at 10.0 m/s and a particle of mass 18.0 kg is moving west at 10.0 m/s, what is the velocity of the center of mass of the pair?

I used the equation
Vcm = P/M
Vcm = [(5.70)(10) + (15)(10)] / [(5.70)+(15)]
Vcm = 10 ms

however, it says that is not the correct answer.
I don't understand why. can someone help?
thanks
Re-write your equation with units. Does everything work out? Are you putting the right numbers in the right places? It's hard to tell without units. Are all your signs correct?

Vcm = P/M where P is (mass kg)(velocity m/s) and where M is the total mass (kg)

Vcm = [(5.70kg)(10m/s) + (15kg)(10m/s)] / [(5.70kg)+(15kg)]
Vcm = 10 m/s

I'm still getting it wrong.