Before colliding, the momentum of block a is +15.0 kg(m/s) and block b -35.0kg(m/s). after block a has a momentum of -12.0kg(m/s). what is the momentum of block b afterwards?

-8 Kgm/s

Explanation:

From the law of conservation of moentum, the sum of momentum before collision equals the sum of momentum after collision. Therefore

Before collision

Momentum =+15 kgm/s+-35 kgm/s=-20 kgm/s

After collision

Momentum=-12 kgm/s +x kgm/s

x-12 kgm/s=-20 kgm/s

x=-20+12=-8 Kgm/s

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