HW Chapter 9 9.8 A wheel is rotating about an axis that is in the z-direction. The angular velocity ω z is –6.00 rad/s at t = 0, increases linearly with time and is +8.00 rad/s at t = 7.00 s. We have taken counterclockwise rotation to be positive. a) Is the angular acceleration during this time interval positive or negative? b) During what time interval, is the speed of the wheel increasing? Decreasing? c) What is the angular displacement of the wheel at t = 7.00 s? 9.13 The rotating blade of a blender turns with constant angular acceleration 1.50 rad/s 2 . a) How much time does it take to reach an angular velocity of 36.0 rad/s, starting from rest? b) Through how many revolutions does the blade turn in this time interval? 9.19 At t = 0 a grinding wheel has an angular velocity of 24.0 rad/s. It has a constant angular acceleration of 30.0 rad/s 2 until a circuit breaker trips at t = 2.00 s. From then on, it turns through 432 rad as it coasts to a stop at constant angular acceleration. a) Through
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