Question

A ball (mass 12 kg) moving at 15 m/s in the +x-direction collides with a ball (mass 36 kg) moving at 5.0 m/s in the +y direction. After colliding, the 12-kg ball moves at 6.0 m/s at an angle of 30°above the +x direction. Afterward, what is the speed and direction of the 36-kg ball? Be sure to include a diagram of the situation.

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Answer 1

you need a and b such that

12*15i + 36*5j = 12*6(.866i+.5j) + ai+bj
180i + 180j = 62.35ai+36bj

a = 180/62.35 = 2.89
b = 180/36 = 5.00

So, the 36kg ball is moving with speed 5.78 m/s
in the direction arctan(5/2.89)=60°