Two carts collide and bounce apart. Cart 1 had a momentum of –6 kg • m/s before the collision. Cart 2 had a momentum of 10 kg • m/s before the collision.

The total momentum before the collision is the sum of the carts’ momenta: –6 kg • m/s + 10 kg • m/s = 4 kg • m/s. Momentum is conserved during the collision, so the total momentum after they bounce apart is also 4 kg • m/s. The correct choice is 4 kg • m/s.

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