Torque

• An external force causes a translational acceleration on an object.
• An external force about the axis is called torque.
• It causes a rotational acceleration of the object.
• That is, the force causes the object to spin faster.
• So, if a resting wheel is hit, it will translate that force into rotational acceleration.
• Assuming there is an opposite force (the axle isn't perfect), acceleration will immediately start to reduce.
• However, it will continue to spin faster until the rotational acceleration, becomes negative.
• It will continue to turn until there is no rotational motion.
• Moment of Inertia (I), as mass translational change I resists rotational change.
• I depends on mass and the shape of the object.
• Torque, moment of inertia and angular acceleration are all vectors. For a ball, they are 2D.