AH Exp – Mechanics 03C – Central force: radius and period of rotation

Aim – To investigate the relationship between the period of rotation and the radius of a circular orbit.

Instructions

The apparatus is set so that the masses rest on an elastic band in the centre of the turntable.
As the turntable rotates, the central force required to maintain the circular motion of the ball is provided by the weight of the masses.
When the turntable is started, it increases in speed and the central force required to maintain the circular motion increases to the point at which the masses just lift off the elastic band.
The marks on the horizontal frame are spaced at 5 cm intervals.

▪ Start the turntable rotating and allow it to increase in speed until the ball just starts to move out. At this point the masses just lift off the elastic band.
▪ Use a stopwatch to measure the period of the ball.
▪ Repeat for different radii of the ball’s orbit.
▪ Draw a graph to show the relationship between the period of rotation and the radius of orbit.

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