The Professional Development Service for Teachers is funded by the Department of Education and Skills under the National Development Plan

T.H.

Investigation of relationship between period and length for a simple pendulum and hence calculate g.

T.H.

PDST Resources for Leaving Certificate Physics 2

Apparatus

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Method

Set up the apparatus as in the previous photo.

Measure and record the distance s from the bottom of the two coins

to the centre of gravity of the bob.

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Method

Hold the bob so that the thread makes an angle of about 5º with the vertical.

Start the timer and release the bob. Record the time t for thirty complete

oscillations.

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Calculate T = t / 30. Graph l against T 2. Draw a best straight line. Find the slope, m, of the graph. Calculate a value for g using g = 4π 2m.

PDST Resources for Leaving Certificate Physics 6

Use the following table to draw a suitable graph and hence find a value for g.

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Note: Don’t forget to draw a new table, with l in metres and T 2 in seconds squared.

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Draw the best straight line and choose two non-data points.

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Find the slope m and calculate g = 4π2m

PDST Resources for Leaving Certificate Physics 10

Sources of error

Take the readings from the metre stick at eye level to avoid the error of parallax.

Do not allow the angle for one oscillation to exceed 10º, otherwise the formula does not apply.

The distance s must be measured from the bottom of the supporting coins bearing to the centre of gravity of

the pendulum bob.

© Tom Healy, Cabinteely Community School, Dublin.