加拿大高三物理预修课教学笔记之Rotational Motion, Torque

1. Describing Rotational Motion

Objectives

• Describe angular displacement.

• Calculate angular velocity.

• Calculate angular acceleration.

• Solve problems involving rotational motion.

Vocabulary

radian

angular displacement

angular velocity

angular acceleration

1.1.  an object rotates, the change in the angle is called angular displacement.

1.2. The angular velocity of an object is angular displacement divided by the time taken to make the displacement.

1.3. Angular acceleration is defined as the change in angular velocity divided by the time required to make the change.

1.4. The following table is a summary of linear and angular relationships.

2. Rotational Dynamics

Objectives

• Describe torque and the

factors that determine it.

• Calculate net torque.

• Calculate the moment of inertia.

Vocabulary

lever arm

torque

moment of inertia

Newton’s second law for

rotational motion

2.1. Lever arm: For a given applied force, the change in angular velocity depends on the lever arm, which is the perpendicular distance from the axis of rotation to the point where the force is exerted.

2.2. Torque is a measure of how effectively a force causes rotation. The magnitude of torque is the product of the force and the lever arm.

2.3. The resistance to rotation is called the moment of inertia, which is represented by the symbol I and has units of mass times the square of the distance.

2.4. Newton’s second law for rotational motion states that angular acceleration is directly proportional to the net torque and inversely proportional to the moment of inertia. This law is expressed by the following equation.

3. Summary

3.1 Describing Rotational Motion

3.2. Rotational Dynamics

3.3 Equilibrium