1.A bicycle tire is spinning counterclockwise at 3.60 rad/s. During a time period ?t = 1.45 s, the tire is stopped and spun in the opposite (clockwise) direction, also at 3.60 rad/s. Calculate the change in the tire's angular velocity ?? and the tire's average angular acceleration ?_av. (Indicate the direction with the signs of your answers.)

(a)the change in the tire's angular velocity ?? (in rad/s) rad/s

(b)the tire's average angular acceleration ?_av (in rad/s²) rad/s²

2.A potter's wheel moves uniformly from rest to an angular speed of 0.25 rev/s in 28.0 s.

(a)Find its angular acceleration in radians per second per second. rad/s²

(b)Would doubling the angular acceleration during the given period have doubled final angular speed? Yes or No

3.A centrifuge in a medical laboratory rotates at an angular speed of 3,550 rev/min. When switched off, it rotates through 48.0 revolutions before coming to rest. Find the constant angular acceleration (in rad/s²) of the centrifuge.

rad/s²

4.The tub of a washer goes into its spin-dry cycle, starting from rest and reaching an angular speed of 7.0 rev/s in 13.0 s. At this point, the person doing the laundry opens the lid, and a safety switch turns off the washer. The tub slows to rest in 11.0 s. Through how many revolutions does the tub turn during this 24 s interval? Assume constant angular acceleration while it is starting and stopping.

rev

5.Human centrifuges are used to train military pilots and astronauts in preparation for high-g maneuvers. A trained, fit person wearing a g-suit can withstand accelerations up to about 9g (88.2 m/s²) without losing consciousness.

(a)If a human centrifuge has a radius of 4.68 m, what angular speed (in rad/s) results in a centripetal acceleration of 9g? rad/s

(b)What linear speed (in m/s) would a person in the centrifuge have at this acceleration? m/s

6.A 38.0-kg child swings in a swing supported by two chains, each 3.02 m long. The tension in each chain at the lowest point is 428 N.

(a) Find the child's speed at the lowest point. m/s (b) Find the force exerted by the seat on the child at the lowest point. (Ignore the mass of the seat.) N (upward)

7.A roller-coaster vehicle has a mass of 560 kg when fully loaded with passengers (see figure).

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