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

PDST Resources for Leaving Certificate Physics 3 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.

PDST Resources for Leaving Certificate Physics 4 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.

PDST Resources for Leaving Certificate Physics 5  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 2 m.

PDST Resources for Leaving Certificate Physics 6 Use the following table to draw a suitable graph and hence find a value for g.

PDST Resources for Leaving Certificate Physics 7 Note: Don’t forget to draw a new table, with l in metres and T 2 in seconds squared.

PDST Resources for Leaving Certificate Physics 8 Draw the best straight line and choose two non-data points.

PDST Resources for Leaving Certificate Physics 9 Find the slope m and calculate g = 4π 2 m

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.