DETERMINATION OF TORQUE

DEFINITION OF TORQUE

Rotating a door

• Where is the best place to apply force to open the door?

• How does the direction of force relate to the axis of rotation?

Torque

Big ideas

What is torque?

What are examples of forces exerting torque in real life?

Big ideas

• How is torque calculated?

• What is the lever arm?

• What is the application angle?

Torque

• Is a measure of how effectively a force causes rotation.

• A measure of a force’s ability to cause rotation

• Generated by an application of force on an object that does not go through the center of mass, axis of rotation

• Application of Torque can result in object changing the rate of spin

Torque

• Units are Nm

• Not Joules (no displacement)

• Direction (clockwise, counter clockwise)

Torque math

• T (Curved top)

• Units Nm (not Joules)

• T = rFsinΘ

• R means______________

• F means _____________

• Θ means ______________

Torque

How to calculate the torque

• Need:

Size of force applied = F

Distance between application of force and pivot point (lever arm length = r )

Angle between force and lever arm (use the smaller of the two angles = Θ)

Torque is larger when:

• A larger force is applied

• The length of the lever arm is increased

• The angle between force and arm is 90°

TYPES OF PROBLEMS INVOLVING TORQUE

Equilibrium of large objects

• Not only must all forces on object be balanced

• The torques on the object must be balanced as well

See-saws and art mobiles

• Example problem

Homework, readings

• Read 201-204

• Try problem 11,13,15 on pg 203