# Physics I- EXPERIMENT III - OBJECTIVES The purpose of this...

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OBJECTIVES The purpose of this activity is to determine the acceleration due to gravity by looking at the graphic of slope of velocity versus time and the position versus time of picket fence dropped through a photogate. APPARATUS 1 Photogate/Pulley System (ME-6838) 2 Picket Fence (ME-9377A) 3 Universal Table Clamp (ME-9376) THEORY A freely falling object has a vertically down ward acceleration. This is known as acceleration due to gravity. From theoretical considerations, we know that the equations of motion give us the following relations. V = V i + gt, (1) and ΔY = V i + (1/2)gt 2 (2) In here, V is the velocity of the object at time t and V i is the initial velocity of the object (which is usually 0). ΔY is the distance traveled in time t and g is the acceleration due to gravity. If V i is zero, from (1) we can write V = gt (3) And from (2) we can write ΔY = (1/2)gt 2 (4) From equation (3) we see that the graph t vs V is a straight line and its slope is g. Same way from (4) we observe that the graph t vs ΔY is a parabola. The graph t 2 vs ΔY is a straight line and its slope is (1/2)g. Thus knowing the values of t, ΔY, and V we should be able to find the value of g (Recall problem solved in experiment no. 1). PROCEDURE Drop a “Picket Fence” (a clear plastic strip with uniformly spaced opaque bands) through a Photogate. Each opaque band on the ‘Picket Fence’ blocks the Photogate beam and the time from one blockage to the next becomes increasingly shorter. Knowing the distance between the leading edge of each opaque band, the DataStudio program calculates the average speed of the Picket Fence from one band to the next. The slope of the graph of average speed versus time gives the acceleration of the falling object.
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