Simple Harmonic Motion (simple pendulum)

Question 1

Equipment

Answer 1

○ Pendulum bob on 2m long string

○ Stand and clamp

○ Pin and blu-tack

○ Metre ruler ○ Stopwatch

○ Two wooden blocks

Question 2

Method

Answer 2

○ Set up the apparatus as shown in the diagram.

○ Adjust the point of suspension so that the distance L from that point to the centre of mass of the pendulum bob is 1.500m.

○ Pull the pendulum to the side and release it so that it has a small amplitude and travels in a straight line. Start the stopwatch when it passes the fiducial marker (pin and blu tack at the centre).

○ Stop the stopwatch after 10 complete oscillations and record this time . Divide T10 T by 10 to find the time period T of the pendulum and record this. 10

○ Decrease the length L by 0.100m and repeat this, reducing L by 0.100m each time down to 0.500m.

○ Repeat the experiment twice more and find and record the mean T for each L

Question 3

Graphs & calculations

Answer 3

Plot a graph of T^2 against L and draw a line of best fit. The gradient will be 4π^2 divided by g.

T = 2π √L/g ⇒ T^2 = 4π^2/g x L

Question 4

Safety

Answer 4

No notable risks

Question 5

Improvements and notes

Answer 5

○ It is recommended to use a small pendulum bob so that it is easier to measure the length to its centre of mass. Additionally, you could measure first the length of the string and then add the radius of the bob onto this to find L.

○ The angle between the string and the downwards vertical at the maximum amplitude should be no more than about 15° for the equations to work.

○ Like the spring experiment, a motion tracker and data logger can be used

Question 6