Angular motion Flashcards
Angular motion
Movement around a fixed point
Examples of angular motion
- Somersault (body)
- Throwing a discuss (arm)
Torque (moment)
- The rotational consequence of a force
- Turning force
What happens to the torque of you increase the size of the force
Increases torque
What happens to the torque if the same force is applied further away from the axis of rotation
Increases torque
How to calculate the moment if force or torque
Moment of force or torque (N/M) =
Force (N) x Perpendicular distance from fulcrum (M)
Newton’s first law to angular motion
A rotating body will continue to tur about its axis of rotation with constant angular momentum unless an external rotational force (torque) is exerted upon it
Sporting example of Newton’s first law to angular motion
Ice skater spinning in the air. They will continue to spin until they land on the ice when an external force is exerted from the ice on the skates
Newton’s second law to angular motion
The rate of change of angular momentum of a body is proportional to the force causing it and the change that takes place in the direction which the force acts
Sporting example of Newton’s second law to angular motion
Ice skater
The greater the torque exerted, the faster the rotation will be
Newton’s third law to angular motion
When a force is applied by one body to another, the second body will exert an equal and opposite force on the other body
Sporting example of Newton’s third law to angular motion
Goalkeeper tips ball over the bar, they throw their arms up which causes the lower part of their legs to go back (reaction force)
Angular displacement
The smallest change in angle between the start and finish point of rotation
How is angular displacement measured
Is measured in degrees and radians
How many degrees is 1 radian
57.3 degrees
Radians
The unit of measurement for angles
Angular velocity
The rate of change of angular displacement
How to measure angular velocity
Angular velocity (rad/s) = Angular displacement (rad) / Time taken (s)
Angular acceleration
The rate of change of angular velocity
How to measure angular acceleration
Angular acceleration (rad/s2) = Chng in angular velocity (rad/s) / Time taken (s)
Moment of inertia
Resistance of a body to angular motion
What 2 things does moment of inertia depend on
1) Mass of the body
2) Distribution of mass around the axis
Mass of the body/object influence on the moment of inertia
The greater the mass, the greater the resistance to change and therefore the greater moment of inertia
Distribution of mass from the axis of rotation influence on the moment of inertia
The closer the mass is to the axis of rotation, the easier it is to turn, because the moment of inertia is low.
Apply the distribution of mass from the axis of rotation influence on the moment of inertia for a diver performing a somersault
Open somersault has a higher moment of inertia than a tucked somersault because n the straight leg position, the distribution of the divers mass is further away from the axis of rotation
Angular momentum
The quantity of rotation a body possesses
How to calculate angular momentum
Angular momentum =
Moment of inertia x Angular velocity
Apply the conservation of angular momentum to a figure skater at the start of theri spin
Arms/legs stretched out
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Increase distance from axis of rotation
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Large moment of inertia
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Large angular momentum
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Slow rotation (spin slower)
Apply the conservation of angular momentum to a figure skater wen they increase angular velocity during the spin
Arms/legs brought in
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Decrease distance from axis of rotation
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Smaller moment of inertia
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Smaller angular momentum
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Fast rotation (spin quicker)
