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The torque on the square plate of mass 120 g and edge 5.0 cm if it rotates about a diagonal with a uniform angular acceleration of 0.2 rad s-2 is y×10-5 N m. The value of y is:

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Important Questions on Rotational Mechanics

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JEE Main
IMPORTANT

A flywheel of moment of inertia 5.0 kg-m is rotated at a speed of 60 rad s-1. Because of the friction at the axle, it comes to rest in 5.0 minutes. Find

(a) the average torque of the friction.

(b) the total work done by the friction.

(c) the angular momentum of the wheel 1 minute before it stops rotating.

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Because of the friction between the water in oceans with the earth's surface, the rotational kinetic energy of the earth is continuously decreasing. If the earth's angular speed decreases by 0.0016 rad per day in 100 years. Radius of the earth is 6400 km and its mass is 6.0×1024 kg. The average torque of the friction on the earth is y×1020 Nm. Calculate the value of y.
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A wheel rotating at a speed of 600 rpm (revolutions per minute) about its axis is brought to rest by applying a constant torque for 10 seconds. The angular deceleration and the angular velocity 5 seconds after the application of the torque is given as α rev s-2 and β rev s-1 respectively. Find the value of αβ.
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JEE Main
IMPORTANT
A wheel of mass 10 kg and radius 20 cm is rotating at an angular speed of 100 rev min-1 when the motor is turned off. Neglecting the friction at the axle, calculate the force that must be applied tangentially to the wheel to bring it to rest in 10 revolutions.
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A cylinder rotating at an angular speed of 50 rev s-1 is brought in contact with an identical stationary cylinder. Because of the kinetic friction, the torques act on the two cylinders, accelerating the stationary one and decelerating the moving one. If the common magnitude of the acceleration and deceleration be one revolution per second square, how long will it take before the two cylinders have equal angular speed?
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IMPORTANT
A body rotating at 20 rad s-1 is acted upon by a constant torque providing it a deceleration of 2 rad s-2. At what time will the body have kinetic energy the same as the initial value if the torque continues to act?
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JEE Main
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A light rod of length 1 m is pivoted at its centre and two masses of 5 kg and 2 kg are hanging from the ends as shown. The initial angular acceleration of the rod is x rad s-2 assuming that it was horizontal in the beginning. Find x.

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IMPORTANT

A light rod of length 1 m is pivoted at its centre and two masses of 5 kg and 2 kg are hanging from the ends as shown. 

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Suppose the rod has a mass of 1 kg distributed uniformly over its length, then find

(a) the initial angular acceleration of the rod.

(b) the tension in the supports to the blocks of mass 2 kg and 5 kg.