Measurement of g the acceleration due to gravity

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Measurement of g, the acceleration due to gravity, using a free-fall apparatus. . T.

Measurement of g, the acceleration due to gravity, using a free-fall apparatus. . T. H. The Professional Development Service for Teachers is funded by the Department of Education and Skills under the National Development Plan

Apparatus . PDST Resources for Leaving Certificate Physics 2

Apparatus . PDST Resources for Leaving Certificate Physics 2

Method § Set up the apparatus as in the photo. § Measure and record

Method § Set up the apparatus as in the photo. § Measure and record the distance s from the bottom of the ball bearing to the metal plate. . § Release the ball bearing. This starts the scaler-timer. § When the ball bearing strikes the plate the scaler-timer stops. § Record the time t on the clock. PDST Resources for Leaving Certificate Physics 3

. Here is a close-up of the release mechanism. Repeat the release of the

. Here is a close-up of the release mechanism. Repeat the release of the ball bearing three times and take the minimum value for t as the clock sometimes starts too early. PDST Resources for Leaving Certificate Physics 4

§ § Graph s against t 2. Draw a best straight line. Find the

§ § Graph s against t 2. Draw a best straight line. Find the slope, m, of the graph. . Calculate a value for g using g = 2 m. Note: We graph t 2 against s as the units of acceleration are m s-2, which makes it easier to remember how to draw a suitable graph. PDST Resources for Leaving Certificate Physics 5

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

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

Note: Don’t forget to draw a new table, with s in metres and t

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

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

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

Find the slope m and calculate g = 2 m . PDST Resources for

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

This is reasonably close to the true value, g = 9. 8 m s-2

This is reasonably close to the true value, g = 9. 8 m s-2 . PDST Resources for Leaving Certificate Physics 10

Sources of Error § Take the readings from the metre stick at eye level

Sources of Error § Take the readings from the metre stick at eye level to avoid the error of parallax. The release mechanism may start the clock too soon giving too high a value for t. . Take a number of readings for t and choose the minimum value. The distance s must be measured from the bottom of the ball bearing to the top of the shock plate. PDST Resources for Leaving Certificate Physics 11