Figure 1
Experiment 3 |
Determination of "g" |
Objective: |
To determine g, the acceleration due to gravity at the Earth's surface. |
Under everyday conditions, one finds that the presence of friction makes it difficult to test the laws of Newtonian mechanics. The airtrack is a device that eliminates most of the friction between a long track and riders that hover on a cushion of air (similar to a hovercraft).
The airtracks and riders must be handled carefully as any damage occurring to them will increase friction and lead to poor results. Take special care to keep all surfaces clean and to not drop the airtrack.
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Figure 1 |
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For a frictionless inclined plane as shown in Fig. 1, the acceleration of the rider is given by a = F/m = mgsinq/m or |
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| a = | g sinq |
(1) |
| = | gh / L |
(2) |
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From simple kinematics, with an initial velocity of zero one finds that the displacement at time t is given by |
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| s = | at2 /2 |
(3) |
| = | ½ (gh/L) t2 by substituting from Equation (2) |
(4) |
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Now by graphing s versus t2 with displacement along the y-axis, one obtains a straight line through the origin. The slope of this straight line will be gh/(2L). To see this, compare equation (4) with y = mx + b, where x is t2 |
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