To measure the centripetal force by whirling it around a horizontal circle, then compare the result with theoretical value FC = m(2r.
1Glass tube (About 15 cm long)
1Slotted weights, with hanger 12 × 0.02 kg
1Nylon thread 1.5 m
1.Attach one end of a 1.5 m length of nylon thread to a rubber bung and thread the other end through a glass tube, a paper marker and a number of weights as shown.
2.First adjust the position of the marker so that it is about 1 cm near one end of the glass tube, and the length of the thread L from the other end of the glass tube to the rubber bung is, say, 0.8 m. Fix the position of the marker using adhesive tape if necessary. First start with M = 0.16 kg (i.e. 160 g).
3.Holding the glass tube vertically, whirl the bung around above your head in a horizontal circle. Increase the speed of the bung gradually and allow it to move out (i.e. let L increases) until the marker is about 1 cm below the lower end of the glass tube. 4.Try to keep the angular speed constant so that the marker is always about 1 cm below the tube throughout. Ask your partner to time 20 revolutions of the bung using a stop watch. Remember to start the stop watch at 0 and stop it at 20. Take one more confirmatory reading and obtain the mean time for 20 revolutions.
5.The horizontal component of the tension T of the string provides the centripetal acceleration of the rubber bung.
As there is no vertical motion, the vertical component of tension(T ) is balanced by the weight of the bung: Tcos[pic]=mg_____ (1) The horizontal component of the tension provides the net centripetal force: Tsin[pic]=mr(2_____ (2)
Substituting r= l sin@ into equation (2), we can find the tension(T ) in the string. Tsin[pic]=m(L sin[pic])(2
The tension (T ) is...