Magnifier: the rule at the bob
String length (clamp)
Changing the length stops the swing. Read the new length off the rule.
The bob
Stopwatch
0.00s
Start as the bob passes the centre, count 20 oscillations, and stop. Write the reading down.
Set at least five lengths between 20 cm and 100 cm. For each, measure l, the length from the pivot to the centre of the bob, and time 20 oscillations, t. Record your readings, then calculate the period T = t / 20 and T², giving T² to three significant figures. Choose the unit for each column heading.
| l/length, pivot to centre of bob | t/time for 20 oscillations | T/period | T²/period squared |
|---|---|---|---|
Plot a graph of T² on the y-axis against l on the x-axis. Choose scales so your points fill at least half the grid in each direction. Draw the straight line of best fit.
Choose a start and a value per large square for both axes, then plot.
Draw a large triangle on your line and use it to determine the gradient G of your line. Give the unit.
The gradient G = 4π² / g. Calculate g, the acceleration of free fall. Give the unit.
State one source of inaccuracy in this experiment.
Suggest one improvement that would reduce the inaccuracy you described in (e).