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| Uniform Circular Motion |
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| In the example discussed under the topic uniform and non-uniform motion we have classified motion along circular track as an example of non-uniform motion. Let us now see why circular motion is considered as non-uniform motion. |
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| Athlete running on a hexagonal
track |
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| The figure shows an athlete running with uniform speed on a track which has a shape of a regular hexagon. |
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| The athlete runs with uniform speed along the segments AB, BC, CD, DE, EF and FA of the track and at the turns he quickly changes his direction of motion to stay on the track, without changing his speed. Similarly if the track was a regular octagon the athlete would have changed the direction of motion eight times to remain on the track. As the number of sides of the track increases, the athlete has to turn more often. Now if we increase the number of sides indefinitely the shape of the track will approach the shape of a circle. Therefore a circle can be considered as a polygon with infinite sides and hence motion along a circular path is classified as non-uniform motion. |
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| Thus, an object moving along a circular track with uniform speed is an example for an accelerated motion because the direction of motion of the object goes on changing at every instant of time. |
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| Differences between uniform linear motion and uniform circular motion |
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| Examples of uniform circular motion |
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| 1) A car negotiating a curve with uniform speed. |
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| Car negotiating a curve |
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| 2) Whirling a hammer in a circle by an athlete before throwing it. |
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An athlete whirling a hammer |
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| 3) An aircraft moving in a loop. |
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| Aircraft
moving in a loop |
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| Suppose an athlete takes t seconds to go once around the circular path of radius r, then the velocity v is given by the relation |
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| distance traveled = circumference of the circle |
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| = 2p r |
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