Acceleration of a steel ball down an inclined plane with metronome.

Acceleration down an inclined plane. When the key switch is held down, 6 V is put across the electromagnet, holding the steel ball at the top. Releasing the switch allows the ball to roll down the inclined plane. As the ball moves down with ever-increasing speed, its position is noted at each tick of the metronome. The angle of the plane has been adjusted so that the distance travelled in the first second is 20 cm; 2 seconds is 80 cm; 3 seconds is 180cm,etc... Note: in order to have the ball pass the marks at the same time as the 'ticks': 1) Vary the time interval of the metronome. (However, 1 second is best.)