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| Angular Variables |
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| Suppose a particle P is moving in a circle as shown below. Let O be the centre and OX be the X-axis. The position of the particle may be described by the angle q. Let the particle move to the position q + dq in a time dt. Assume that the particle keeps changing its position. Thus, we can define a variable called angular velocity which is nothing but the rate of change of angular position. |
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 Units of angular velocity are radsec-1 |
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 When the angular velocity remains constant with time, the particle is said to be performing uniform circular motion. |
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| If the angular velocity changes with time, then we can define another
variable called a (or alpha) which is the symbol
for angular acceleration acceleration. |
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| If w1 and w2 are the angular velocities at time t = t1 and t = t2 respectively, then average angular acceleration is given by |
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| In the differential form |
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| It is clear from the above stated formula that angular acceleration is the rate of change of angular velocity. |
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 Its unit is radsec-2. |
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| Consider the same situation as in the above section. |
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| Let the particle move from P to P1 with velocity v in time dt. |
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| Let dq be very small. |
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| We know that |
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