Investigating motion using video processing software.

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Experiment 6:  Investigating motion using video processing software

Part 1

Method

The web camera was setup with the laptop connected.  The web cam made a recording of firstly, a ball being thrown in the air next to a vertical ruler.  On the computer program, from frame to frame the position of the ball is recorded.  A displacement-time graph is produced from this data.

Results

Also see graphs

This graph shows a of squash ball thrown up vertically in the air.  The period T is 0.91 secs.  As the ball is thrown it reaches a peak being 1.057m, the displacement then decreases as gravity acts on the ball.  

     If tangents are drawn, the gradient for the steep incline of displacement on the left side of the graph = 0.865 / 0.27 = 3.20  

     This gradient also calculates the mean speed, as speed = dis. / time.  Thus the mean speed from 0 – 0.27 secs = 3.20 m/s

     As the ball reaches the peak in displacement, the speed is expected to decrease.  This is due to the downward force of gravity.  If a tangent is drawn at the peak of the graph, a gradient and hence speed can be worked out.

                       = 0.13 / 0.17 = 0.78 m/s

Thus, the prediction is true.  In addition the speed is expected to increase as the ball accelerates with the force of gravity.  So if a gradient/speed is worked out for the steep decline in displacement,  = 0.24 / 0.75 = 3.125 m/s

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A graph of speed against time has also been produced, which is non-linear.   This graph shows that the ball gains speed from zero out of the throwers hand.  This speed increases sharply, but begins to fall as the force of gravity acts on it.  As the ball reaches its peak in displacement, the speed decreases to 0m/s at its highest peak of 1.057m.  However, the ball gains speed once more as the force of gravity accelerates the ball towards the ground.  The graph shows this as the curve inclines steeply from 0m/s.

     However, if tangents are ...

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