With the turntable spinning at about 30 rpm, the masses will swing outward. Sighting downwards, students can determine the change in separation as the difference between the initial separation with the two-meter stick and current radius of rotation.
Given this information and one other known the students can find many different things about the situation. They can determine, from the acceleration of gravity and the centripetal acceleration resulting from tension in the string (mV2/r) the angular velocity of the turntable. Given the turntable they can calculate g and compare to the accepted value.
Given the mass they can find the tension in a string. This can be checked by using pulleys on the ends of the crossbar and attaching the strings to spring force gauges. An allowance must be made for the stretch of the force gauge as to the hanging length of the masses.