Experiment to find gravity from a
Pendulum
Surya Tahir/BTEC National
Diploma/Pendulum Experiment
Covers objectives:
• P3 – demonstrate the ability to plot a linear
graph using scientific data
• P3 – Calculate the rate of change by the most
appropriate method
• D1 – determine the size and influence of
errors on final calculations
Surya Tahir/BTEC National
Diploma/Pendulum Experiment
Stage 1
• Draw up a table with the following headings:
Length (m) Time (1st)
for 10
swings
÷ 10
Time (2nd)
for 10
swings
÷ 10
Average
length of
time (T)
1.
2.
3.
4.
5.
Surya Tahir/BTEC National
Diploma/Pendulum Experiment
T²
Stage 2
•
•
•
•
•
•
Set up equipment safely
Measure string at a short length
One person to time 10 pendulum swings
Partner to record data
Do this twice
Measure 5 different lengths of string
Surya Tahir/BTEC National
Diploma/Pendulum Experiment
Stage 3
• On graph paper plot length of pendulum (l)
against T²
• You should have 5 sets of data points
• You can now work out the gradient by
choosing 2 suitable points and calculating :
T² / l
Surya Tahir/BTEC National
Diploma/Pendulum Experiment
Stage 4
• We can now find an estimate for gravity by
comparing the formula for a straight line:
Y=mx+c
• With the formula for one complete oscillation
of a pendulum:
T= 2π√(l/g)
Or T² = 4 π²l/g
Surya Tahir/BTEC National
Diploma/Pendulum Experiment
Stage 4 continued..
• So gravity =
• 4 π² ÷ gradient from graph
Surya Tahir/BTEC National
Diploma/Pendulum Experiment
Stage 5 -comparison
• How close were you?
•
•
•
•
In the northern hemisphere..
Acceleration due to gravity…
Is…
9.81m/s²
Surya Tahir/BTEC National
Diploma/Pendulum Experiment
Stage 6 – Evaluation and write-up
**Question 1
Work out the actual error and percentage error
between your value and the actual value for
gravity
**Question 2
• Consider why we took values for 10 pendulum
swings, and why this was done twice
Surya Tahir/BTEC National
Diploma/Pendulum Experiment