Chapter # 11 (Rotation)

1- A disk of radius 20 cm rotating at 42 rad/sec stops (assume constant deceleration) after 10 sec. Through how many radians does the disk turn during this time? 210 rad


2- A disk is rotating about an axel through its center O when two forces F1 = 10 N and F2 = 15N are applied on it as shown in Fig. The moment of inertia of the disk about O is 0.036 kg.m**2. If the system starts from rest, find the angular speed at time = 3.0 s.  [100 rad/s]



3- A uniform rod of length L= 0.98 m and mass M=3.0 kg is free to rotate on a frictionless pin through one end (See Fig). The rod has an angular speed of 4.0 rad/s when it was in the horizontal position. What is the angular speed at its lowest position?  [6.8 rad/s]




4- The four particles in Fig (6) are connected by rigid rods of negligible mass. Calculate the moment of inertia of this system about the x axis. [63 kg.m**2]






5- A wheel has a moment of inertia 12 kg*m**2 about its axis of rotation. As it turns through 5.0 rev, its angular velocity increases from 5.0 rad/s to 6.0 rad/s. If the net torque about the axis of rotation is constant, its value is: [2.1 N*m]


6- A disk has a moment of inertia 6.0 kg*m**2 about a fixed axis of rotation. It has a constant angular acceleration of 2.0 rad/s**2. If it starts from rest, the work done during the first 5.0 s by the net torque on it is: [300 J]


7- A wheel, starting from rest, turns through 8.0 revolutions in a time interval of 17 s. Assuming constant angular acceleration, what is the angular speed of the wheel at the end of this time interval? [5.9 rad/s]


8- Four identical particles, each with mass m, are arranged in the xy plane as shown in figure. They are connected by light rods to form a rigid body. If m=2.0 kg and a=1.0 m, the moment of inertia of this system about the y-axis is: [12 kg*m**2]






9- A wheel with a moment of inertia of 5.0 kg*m**2 and a radius of 0.25 m rotates about a fixed axis perpendicular to the wheel and through its center as shown in figure 10. A force of 2.0 N is applied tangentially to the rim. As the wheel rotates through one revolution, what is the work done by the force ? [3.14 J]