t is made sure that the position of the cross arm and radial indicator allows the mass to hang directly over the indicator when the spring is released. The diameter of the shaft and the distance from the shaft to the indicator are then measured and recorded. Hand is then used to spin the shaft until the hanging weight passes directly over the indicator. With the radius held constant, the time taken by 50 revolutions is recorded. From this, frequency of the motion can be determined and hence centripetal force on the mass.
To determine the actual force required to stretch the spring enough to hold the weight over the indicator, a string is connected to the mass and passed over to the pulley. Weights are then added to the end of the string until the mass is positioned over the indicator. The value of force obtained will be correct and can be used in calculating the uncertainty in the value of centripetal