Inclined plane

A box is released from rest at the top of a 30 degree ramp. The box slides down the ramp, dropping a vertical distance of 1.5 m to the floor. How long does it take to reach the floor? Neglect friction.

The ramp is 3.0 m long. If we knew the acceleration of the box we could use the constant acceleration equations to find the time.

By analyzing the forces on the box the acceleration can be determined. Once again, the key is to construct a good free-body diagram.