Torque and Moment of Inertia

Torque

Torque

• A rotational force as a result of an applied linear force

•  $\tau=rF\sin\theta$  

•  $\tau=I\alpha$  

Multiple Choice

The product of the force times the lever arm; the movement of the force about the axis is:

• torque

• lever arm

• rotational inertia

• angular momentum

Multiple Choice

When an object is experiencing a net torque

• it is in dynamic equilibrium.
• it is in static equilibrium.
• it is rotating.
• it is translating.

Torque

is a pivoting force due to an object that is pinned at a certain location

Multiple Choice

Is torque independent of the location of the origin?

• Yes, always.
• Yes, as long as the origin is either in the center or on one end.
• No, you always need to specify the origin.

 $\sin\theta$  

• Perpendicular $\sin\ \theta=1$   

• parallel   $\sin\theta=0$   

Multiple Choice

A force is applied to a wrench at various angles which angle results in the least amount of Torque on the object?

• 90 degrees

• 45 degrees

• 180 degrees

• 10 degrees

Fill in the Blanks

Two children are trying to balance on a 3.2m see-saw. One child has a mass of 40kg the other has a mass of 50kg. If the see-saw is balanced perfectly in the middle and the 40kg child is sitting at one end of the see-saw, how far from the center should the 50kg child sit so that the system is perfectly balanced

Multiple Choice

Which applied force has the most Torque?

• F₁

• F₃

• F₄

• F₅

Inertia

• The resistance to acceleration of a body when responding to all types of force

• mass determines the force needed for a desired acceleration

•  $I=mr^2$  point mass

Fill in the Blanks

A rod is rotated about the center axis with a length of 2.4 m and a mass of 20 kg. A Torque of 76 Nm is achieved. What is the resulting acceleration of the rod? 2 sig figs

Multiple Choice

What does the rotational inertia describe? 

• The average position of mass in an extended object.
• How the mass of an object is distributed 
• How a force can rotate an object.
• The tendency of an object to move in a straight line.

Multiple Choice

What happens to her angular velocity when a figure skater brings in her arms?

• Increases her angular velocity
• Decreases her angular velocity
• Has no affect

Multiple Choice

What happens to her rotational inertia when a figure skater brings in her arms?

• Increase her rotational inertia
• Decrease her rotational inertia
• has no affect