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## Homework Statement

:A cart 'C' mass of 2 tonnes is launched at 10m/s towards Cart 'B' which is 3 tonnes and moving at 12.5m/s. The angle between their paths of motion is 90 degrees. When the 2 carts collide, they remain stuck together. what is the velocity of the stuck together cart 'CB'

assuming no friction.

## Homework Equations

P=mv

Pfinal=Pinitial

c= √b

^{2}+c

^{2}

## The Attempt at a Solution

what i assumed was you could create a right angle triangle, with momentum of Cart C as one side, momentum of Cart B as another and the hypotenuse would be momentum of cart CB

So therefore:

Pbc= √Pb

^{2}+Pc

^{2}

Pbc=√(3000x12.5)

^{2}+(2000x10)

^{2}

Pbc=√1406250000+400000000

Pbc=4250

Pbc=m(c+b)v

4250=5000v

v=8.5m/s

but apparently the answer is 7.8m/s

what have i done wrong?