Biomechanics: Angular Motion Flashcards
Define angular motion
Movement/rotation around a fixed point or axis
What is an off-centre force also referred to as?
An eccentric force
What does angular motion occur as a result of?
Torque
How can moment of force/torque be calculated?
Force x Perpendicular distance from the fulcrum (newton metres) (newtons)
Describe Newton’s 1st Law of Angular Motion
A body will continue rotating/spinning with a constant angular velocity unless acted upon by an external torque/rotational force.
Describe Newton’s 2nd law of angular motion
The rate of change of angular momentum of a body is directly proportional to the force causing it and the change takes place in the direction in which the force is applied.
Describe Newton’s 3rd law of angular motion
When a force is applied by one body to another, the second body will exert and equal and opposite force on the other body.
Define angular displacement
The smallest change in angle between the start and finish point of a rotation
What is the unit of measurement for angular displacement
Radians/r or degrees /°
What is the definition for angular velocity?
The rate of rotation around an axis of rotation
Define angular acceleration
The rate of change of angular velocity
What is the unit of measurement for angular velocity?
Radians per second (rad/s)
What is the unit of measurement for angular acceleration?
Rad/s2
Identify A, B and C in the picture
A - Angular Momentum
B - Angular Velocity
C - Moment of Inertia
Define angular momentum
Angular momentum is the quantity of rotation a body possesses and is a product of moment of inertia and angular velocity, so remains constant.
Define angular velocity
Angular velocity is the rate of rotation of a body around its axes of rotation.
Define moment of inertia
Moment of inertia is a body’s reluctance to rotation/
What is the relationship between angular momentum, angular velocity and moment of inertia
Angular Momentum = Angular Velocity x Moment of Inertia
What two factors does moment of inertia depend upon?
Mass of the body/object
Distribution of mass from axis of rotation
Explain how mass of an object affects moment of inertia
The greater the mass, the greater the resistance to change and therefore, the greater the moment of inertia
Explain how the distribution of mass from an axis of rotation impacts moment of inertia
The closer the mass is to the axis of rotation, the lower the moment of inertia. The further away mass is from the axis of rotation, the higher the moment of inertia.
