Two carts, of inertias m1 and m2, collide head-on on a low-friction track. before the collision, which is elastic, cart 1 is moving to the right at 14 m/s and cart 2 is at rest. after the collision, cart 1 is moving to the left at 6 m/s . if the positive direction is from left to right, what is the speed of cart 2 after the collision?