Friction on Ice

Friction occurs even on smooth surfaces such as ice, otherwise skating on ice would not be possible. When a figure skater skates on ice, it is the friction between the inside of the blade and the ice which causes the resistance that allows for motion in the opposite direction, propelling the skater forward.

Moment of Inertia (cont)

The moment of inertia depends on both the mass of the object and the distribution of this mass around the axis of rotation. For this reason, figure skaters often pull their arms in during a turn in order to decrease their moment of inertia and increase their speed.

Motion Resistance

A spin performed by an ice skater is the result of more than just torque. Inertia, the skater's bodily resistance to a change in state also comes into effect by decreasing the speed of the skater. In situations such as making a turn while ice skating where the motion is rotational, this factor is called the "moment of inertia."

Skating on Ice

Torque is what allows a figure skater to skate on ice. A skater pushes one of his/her feet against the ice in order to exert a torque on his/her body and thereby initiates a spin.

Designing a Door

Torque has to be taken into account in the design and creation of a door. Because the torque of a force is greater when it is applied along a larger distance from the axis of rotation (and therefore the force is more effective) door knobs are placed on the side opposite the door hinges.

Torque, Clarified

It is important to note that torque is not always determined by the total force applied on an object. Instead, it is only the force that is perpendicular to the lever arm that is taken into account in the calculation.

Torque (cont)

The torque of a force is found using this simple formula:
T = Fd, which means that the torque equals the distance from the axis of rotation to the place where the force is applied (d) multiplied by the magnitude of the force (F). Maximizing the torque of a force has many real-world benefits, so being able to calculate it is beneficial.

Intro to Torque

Torque is a rotational force. It is, in a way, a measure of the force causing an object to rotate around a fixed axis.