Question

Two carts collide on a low-friction track. Cart 1 has an initial momentum of +10 kg⋅m/sι^ and a final momentum of -5.0 kg⋅m/sι^ . If cart 2 has a final momentum of -7.0 kg⋅m/sι^ , what was its initial momentum?

Answer 1

According to the saving of the momentum, the total momentum before collision is equal to the total momentum after collision

in symbols:

$P_{i1}+P_{i2}=P_{f1}+P_{f2}$

thus

$10+P_{i2}=(-5)+(-7)$

then, the initial momentum of the second cart

$P_{i2}=(-7)+(-5)+(10)=-23m/s$

Answer 2

Due to the Law of Conservation of Momentum we have;

P1i+P2i=P1f+P2f

10+P2i=-5-7

P2i=-22

So Cart 2 initial momentum is -22kg*m/s^2