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The motor of an engine is rotating about its axis with an angular velocity of `100`rpm. It comes to rest in `15s`, after being switched off. If angular deceleration is constant, what is the number to revolutions made by it before coming to rest ? |
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Answer» Here, `n_(1) = 100"rpm" = (100)/(60) rps`, `n_(2) = 0, t = 15 s, alpha = ?, n = ?` `alpha = (omega_(2) - omega_(1))/(t) = (2pi(n_(2) - n_(1)))/(t)` `= (2pi(0-(100)/(60)))/(15) = - (2pi)/(9) rad s^(-2)` `theta = omega_(1)t + (1)/(2) alpha t^(2)` `= 2pi xx (100)/(60) xx 15 + (1)/(2) (-(2pi)/(9)) (15)^(2)` `= 50pi - 25 pi = 25 pi` Number of rotations made, `n = (theta)/(2pi) = (25pi)/(2pi) = 12.5` |
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