Rotational Kinematics
Torquing
MOI & KE
Work + Power
Misc.
100
What is the value of the angular acceleration of the second hand of a wall clock?
0 rad/s2
100
Two identical rods are pivoted at one end. Rod A has a 30 N force applied at its midpoint, perpendicular to the rod. Rod B has a 20 N force applied at its end, perpendicular to the rod. Which rod experiences the greater torque about the pivot?
Rod B
100
An amorphous mass rotates about an axis through its center of mass. The axis is then shifted to a parallel axis close to the edge of the mass. Which change occurs?
a. The moment of inertia increases
b. The moment of inertia decreases
c. The moment of inertia remains the same
d. The angular velocity must decrease
a. The moment of inertia increases
100
A person spins a large grindstone by placing her hand on its edge and exerting a 180N force through 1 rad. The force is kept perpendicular to the grindstone’s 0.32 m radius at the point of application, and the effects of friction are negligible. What is the final rotational kinetic energy after this motion?
57.6J
τ=rF=(0.32 m)(180 N)=57.6N
W=τθ
100
Write the equasion for the parallel axis theorem
Is=Icm+md2
200
A solid disk of radius 0.30m rolls without slipping down a ramp. The center of mass reaches a speed of 2.0 m/s. What is the angular velocity of the disk?
6.7 rad/s
v=omega*r
200
A rigid object has a moment of inertia of 2.0 kg·m^2 about a fixed axis. A constant net torque of 6.0 N·m acts on the object. What is the angular acceleration?
3 rad/s2
200
A solid disk has mass 2.0 kg and radius 0.30 m. What is the moment of inertia about a parallel axis 0.20 m away from the center?
0.17 kg·m2
Icm=0.5mr2
200
A solid disk (I=0.5m*r2) of mass 2kg and radius 0.4m is initially rotating at 0.5 rad/s. A constant torque of 1.8 Nm is applied to the disk about its central axis. How much work is done by the applied torque in 6 revolutions?
68J
W=τθ
200
A rigid object rotates about a fixed axis. Its angular velocity increases, but the axis of rotation does not change. Which quantity remains constant?
a. Angular momentum
b. Rotational kinetic energy
c. Moment of inertia
d. Torque
C
300
A wheel starts with an angular velocity of 2 rad/s and undergoes a constant angular acceleration of 1.5 rad/s2. How much angular displacement does the wheel undergo in the first 4 s?
20 rad
300
A force of 40 N is applied to a wrench of length 0.50 m at an angle of 30 degrees relative to the wrench. What is the magnitude of the torque?
10Nm
300
A “dumbbell” rotates about a fixed axis through its center. It consists of two identical point masses of 0.40 kg each connected by a uniform rod of mass 0.20 kg and length 0.60 m. The system rotates in a plane about an axis through the midpoint of the rod, perpendicular to the rod. If the dumbbell rotates at 10 rad/s, what is its rotational kinetic energy?
3.9J
MOI=0.078 kg*m2
300
A spinning top with a moment of inertia of 0.001 kg m/s increases in angular velocity from 1 rad/s to 15 rad/s in 1.5 seconds. What is the instantaneous power delivered to the object at t=0.25 seconds?
0.031 W
P=τω= Iαω
ω(0.25)=3.33 rad/s
300
Where is the 10kg mass so the system wont rotate?
2.4M