Angular motion

Angular motion

Movement around a fixed point

Torque

The rotational consequence of a force

Radian

The unit of measurement for angles. One radian = 57.3 degrees

Angular displacement

The smaller change in angle between the start and finish point of rotation

Angular velocity

The rate of change of angular displacement

Angular acceleration

The rate of change of angular velocity

Angular momentum

The quantity of motion that the body has during rotation (spin)

Moment of inertia

the resistance of a body to a change of state when rotating

moment

The turning effect produced by a force measured in newton metres (Nm)

Angle of release

The flight path of a projectile in the absence of air resistance

Parabolic curve

The flight path of a projectile in the absence of air resistance

What causes angular motion?

Torque (a turning force) an increased force = increased torque

What does application of the same force further from the axis of rotation cause?

Increased torque

What equation links torque, force, and perpendicular distance from fulcrum?

Moment of force or torque = force x perpendicular distance

What is torque measured in?

Newton meters

What is force measured in?

Newtons

What is the angular analogue of newton’s first law?

A rotating body will continue to turn about its axis of rotation with constant angular momentum unless an external rotational force (torque) is exerted upon it

What is the angular analogue of Newtons second law?

The rate of change of angular momentum of a body Is proportional to the force (torque) causing it and the change that takes place in the direction in which the force (torque) acts

What is the angular analogue of Newtons third law?

When a force (torque) is applied by one body to another, the second body will exert and equal and opposite force (torque) on the other body

What is angular displacement measure in?

Degrees and radians

What is 1 radian?

57\.3

What is inertia?

Resistance to change in motion

What is moment of inertia?

The resistance of a body to angular motion (rotation)

What does moment of inertia depend on?

* the mass of the body
* the distribution of mass around the axis

how does mass affect moment of inertia?

the greater the mass the greater the resistance to change, therefore the greater the moment of inertia

How does distribution of mass from the axis affect moment of rotation?

The closer the mass to the axis of rotation, the easier it is to turn - the moment of inertia is low

* increasing distance of distribution of mass from the axis will increase the moment of inertia

How is moment of inertia important to improve sprinting technique?

* upper leg action during sprinting rotates around the hip (leg back = drive = extending)
* = leg has high moment of inertia as mass = distributed away from the hip joint
* Sprinter recovers front leg bringing mass of leg closer to hip joint = reduces moment of inertia
* Can bring leg through quicker to start drive phase
* = high knee lift is important

what does angular momentum depend on?

Moment of inertia and angular velocity

What is the relationship between angular momentum, moment of inertia and angular velocity?

Angular momentum = moment of inertia x angular velocity (these are inversely proportional)

What does it mean by ‘angular momentum is a conserved quantity’?

It means it stays constant unless an external torque (force) acts upon it (N 1st law)

What is the principle of angular momentum?

Angular momentum remains constant, if moment of inertia decreases, angular velocity increases and vice versa

* body will still rotate the same amount but resistance to rotation/ rate of rotation may change