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

1.

2.

3.

4.

5.

Time (2 nd ) for 10 swings ÷ 10 Average length of time (T) T²

Surya Tahir/BTEC National Diploma/Pendulum Experiment

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= 2 π √( l /g) Or T² = 4 π² l /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