A flywheel is spinning with its axle pointing along the east-west direction. You

Question

A flywheel is spinning with its axle pointing along the east-west direction. You are standing west of the flywheel facing toward it. You notice that a point at the top of the flywheel is moving toward your left.

a) What is the direction of the flywheel's angular velocity?

b) If the flywheel's angular speed is increasing, what is the direction of its angular acceleration?

c) If the flywheel's angular speed is decreasing, what is the direction of its angular acceleration?

d)If the flywheel's angular speed is decreasing, what is the direction of the tangential acceleration of a point at the top of the flywheel?

Explanation / Answer

x axis along east...i

y along north....j

z along upward ......k

v = yj

r = zk

1)W = rxv = k x j = -i ....along west

2) alfa = dW/dt.....dW is positive .so,alfa is positive...along alfa is in same direction as dW .i.e west.....-i

3) alfa = dW/dt.....dW is negative .so,alfa is negative...along alfa is in opposite direction of dW .i.e east......i

4) a = alfa x r = i x k = -j along -y axis .......along south

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