The object of this experiment is to show that the time of swing of a simple pendulum depends only on the length of the pendulum, and to determine the value of the gravitational constant (g) using a simple pendulum.
1. 1 Plumb Bob and Line. (Item P11)
2. 1 Adjustable Hook. (Item P6 )
3. 2 Knurled Nuts. (Item P1 ) To identify these
4. 1 Diamond Knurled Screw. (Item P3 ) items see Universal
5. 1 100 gm Mass. (Item P7 ) Parts List.
6. 1 Length of Cord (approx. 70cm.). (Item P18)
7. Stop Watches.
8. Metre Rule
1. Secure the mounting panel in the vertical position.
2. Position the adjustable hook (P6) in hole 9K and secure with nut (P1).
3. Place the diamond knurled screw (P3) through hole 15I and secure with nut (P1).
4. Take a soft pencil and a metre rule and draw a horizontal line on the mounting panel, passing through the centre of hole 9J, and mark it ‘0’ (i.e. zero).
5. Now make similar lines below it at 13, 16, 25, 28 and 36cm from zero and mark these figures by the lines. (It is helpful to remember that the holes in the panel are spaced 5cm apart).
6. Lengthen the cord on the plumb line (P11) by approximately 70cm, using a suitable knot so that it can be removed when the experiment is completed.
1. Slide the rod so that the hook on item P6 is exactly in line with zero (i.e. hole 9J).
2. Take the plumb bob and pass the cord once around the hook, and then clamp the free end under the head of the screw (P3). The plumb bob has a dot stamped on its largest diameter which represents the centre of gravity. For Test 1 this dot should be positioned in line with your 16cm mark, thus giving a pendulum length (L) equal to 16cm.
3. Set the pendulum swinging with an amplitude (see apparatus diagram) of approximately 5cm on either side of the rest position. You can judge this by the holes in the mounting panel.
4. RECORD THE TIME FOR 20 COMPLETE SWINGS, a complete swing being from one extreme position to the other and back again.
5. Repeat each experiment two or three times to obtain an average result.
6. REPEAT for amplitude of 10cm.
7. Add a 100g mass to the plumb bob. This will slightly alter the centre of gravity position and instead of being at the centre dot on the plumb bob it will now be at the bottom of the 100g mass where it rests on the bob.
8. Adjust the cord so that the bottom of the 100g mass is in line with the 16cm mark.
9. RECORD THE TIME FOR 20 SWINGS, with amplitudes of 5 and 10cm.
1. Keep the 100g mass on the plumb bob, but lower it by the cord until the bottom of the 100g mass is in line with the 25cm mark.
2. Set the pendulum swinging with an amplitude of approximately 10cm and RECORD THE TIME FOR 20 SWINGS.
3. Lower the bob until the length of pendulum is 36cm and RECORD THE TIME FOR 20 SWINGS.
4. Before you move the pendulum from this position, mark the cord at the suspension point on the hook with a pencil or pen, then lower the cord until the mark on the cord is in line with the 13 cm mark on the panel. This will now give a pendulum length of 36 + 13 = 49cm.
5. RECORD THE TIME FOR 20 SWINGS of the pendulum of length (L) 49cm.
6. Lower the cord until the mark on the cord is in line with the 28cm mark on the panel. This will now give a pendulum length of 36 + 28 = 64cm.
7. RECORD THE TIME FOR 20 SWINGS of the pendulum of length (L) 64cm.