"g" by Pendulum
Objective: Measure "g" using the period (T) of a pendulum.
Equipment: pendulum, pressure
clamps, meter stick, stopwatch, vernier caliper
Methods:
1. Sketch and label the set up.
2. Determine the length (L) of
the pendulum to the center of the ball (string + 2 diameter of ball).
3. Swing the pendulum with an arc
<10o
from the vertical. Countdown “3-2-1-0”
before starting the stopwatch
4. Record the total time for 50
complete swings.
5. Repeat for 5 other lengths of
the pendulum between 0.2 m and 2 m.
Analysis:
1. Calculate the period (T) for one
swing to the nearest 0.01 second for
each pendulum length, then T2.
2. Plot the data of L vs T2
(L on the y-axis). Calculate the slope
with units. What does the slope represent? Calculate g using your slope and the
equation derived in class.
3. Calculate a percent error
using 9.804m/s2 for Brockport.
4. Using your graph,
predict L by interpolation when T = 1.0s; 2.0s (remember: your x-axis is T2).
5. Why did we use 50 swings to
determine T rather than 1or 2 swings?
6. How would a 1 second period (T)
on earth be different for your pendulum on the moon? (gm = 1.67 m/s2).
7. What length pendulum on
the moon would produce a 2.0 s clock?
8. Grandfather clocks have a 2.0
second swing. If a 3.0 second clock
(great grandfather) could be made, how tall would a room have to be?
9. How would a pendulum bob of different
mass affect your results?
Back to the Brockport High School Science Department