Q23 of 149 Page 195

A square plate of mass 120 g and edge 5.0 cm rotates about one of the edges. If it has a uniform angular acceleration of 0.2 rad/s2, what torque acts on the plate?

The torque on the plate acted by the mass of 120g is


Given


The mass of the plate is 120g, the edges of the square is 5.0 cm and the angular acceleration is 0.2 rad/sec2


Formula Used


The formula used is that of a torque which tells us the mechanics of force which helps the object to rotate. The formula is



and



where


F is the force applied on the object; r is the radius of the object turning. Turning angle is given by , I is the moment of Inertia, L is the length at which the force is applied.


Explanation


The moment of Inertia of the plate is known as




Now putting the values in the respective variables of mass and edge length is



Hence, the torque produced by the plate is calculated as




More from this chapter

All 149 →
21

A cubical block of mass m and edge α slides down a rough inclined plane of inclination θ with a uniform speed. Find the torque of the normal force acting on the block about its centre.

 22

A rod of mass m and length L, lying horizontally, is free to rotate about a vertical axis through its centre, A horizontal force of constant magnitude F acts on the rod at a distance of L/4 from the centre. The force is always perpendicular to the rod. Find the angle rotated by the rod during the time t after the motion starts.

 24

Calculate the torque on the square plate of the previous problem if it rotates about a diagonal with the same angular acceleration.

 25

A flywheel of moment of inertia 5.0 kg-m2 is rotated at a speed of 60 rad/s. 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 and (c) the angular momentum of the wheel 1 minute before it stops rotating.