Object a with a mass of 1.5 kilograms is moving with a velocity of 11.2 meters/second (moving in the x direction). it has a perfectly elastic collision with stationary object b that has a mass of 4.5 kilograms. after the collision, object b travels with a velocity of 5.6 meters/second. what is the final velocity for object a?

Conservation of momentum => momentum before collision = momentum after collision

Momentum before collision = momentum of object a = m*v = 1.5 kg * 11.2 m/s

= 16.8 N*s (in x direction)

Momentum after collision = momentum of object a + momentum of object b =

= 1.5 kg * v + 4.5 kg * 5.6m/s = 1.5kg*v + 25.2 N*s

= > 16.8 = 1.5v + 25.2 => 1.5v = 16.8 - 25.2 = -8.4

=> v = -8.4 / 1.5 = -5.6 m/s

The negative sign means that the object a went back after the collision.