400882 Introduction to Biomechanics - Torque

What is meant by the term 'static equilibrium'?

• In static equilibrium, all external forces are balanced and the body is motionless.

i.e. acceleration = 0 ...or ΣF = 0

• similarly in angular situations, if all external torques are balanced then there is no rotation

i.e. ΣT = 0

Define Torque; provide its symbol/s and unit of measurement.

• Torque is not force, it is the consequence of force applied in a particular way (the effectiveness of a force causing rotation around a specific axis)

• Torque is the rotary or turning effect of a force about an axis of rotation (also known as moment of force)

• The force needs to be applied outside the line of the center of mass

• CW = -ve ... CCW = +ve (Think about right hand rule - thumbs up +ve & thumbs down -ve)

• Torque = Force x (r or d)

• Units are Nm (newton metres)

The perpendicular distance from the line of action of a force to the axis of rotation is known as the what?

Moment arm (r or d)

Under what circumstances are torques produced?

Torque is produced when a force is applied outside the centre of mass

You have a flat and are having great difficulty loosening a nut on your car tire. Explain how you could generate greater torque so that the nut can be loosened.

Get a longer spanner or hold the spanner as far from the nut as possible

Explain why it is easier to push open a door by applying the force further from the hinge side of the door.

Because if T = Fd⊥then for the same F a longer d⊥ will produce more torque.

Explain the convention used to describe the direction of rotation caused by applying a torque.

The right hand rule - the directions that the fingers curl on the right hand is the direction that rotation is occurring and the direction of the thumb can describe the direction with a straight arrow

Explain how / why the resistance changes during a bicep curl and at which point the resistance is greatest.

Resistance changes during a bicep curl because the moment arm length changes throughout the movement in respect to the force in the direction of gravity. The resistance is greatest when the d⊥ of the forearm is the greatest. (parallel to the ground)