Biomechanical Movement Flashcards
What is Angular motion?
- Angular rotation refers to rotation
- Rotation is movement around a fixed point/axis
- Can involve the whole body or just an arm or leg
- In a runner, they run in a straight line but have large amounts of rotation in their arms and legs.
What is an eccentric force?
An off-centre force,
When does Angular motion occur?
Angular motion occurs when a force is applied outside the centre of mass.
What is the transverse axis?
- The transverse axis runs from side to side across the body.
- A somersault rotates a body in a transverse axis.
What is the Sagittal axis?
- The Sagittal axis runs from front to back.
- A cartwheel rotates around the sagittal axis.
What is the Longitudinal axis?
- The longitudinal axis runs from top to bottom.
- A multiple spin in ice skating rotates in a longitudinal axis.
What is torque?
Often called the moment, torque is the turning force and causes angular motion to occur.
Torque causes an object to turn about it’s axis of rotation. It is dependent on 2 things:
1) The greater the size of the force, the greater the torque.
2) Application of the same force further away from the axis, will increase torque.
How do you calculate ‘moment of force’?
Moment of force/torque (Nm)= Force (N) X Perpendicular distance from the fulcrum (M)
What are the 2 things ‘moment of force’ can be?
- Resistance arm
- Effort arm
What is the resistance arm?
Shortest perpendicular distance between fulcrum and resistance.
What is the effort arm?
Shortest perpendicular distance between fulcrum and effort.
What is the definition of speed?
Speed can be defined as the rate of change of a position and can be calculated as: speed (m/s)= distance covered (m)/ time taken (s)
What type of quantity is speed?
Scalar quantity
What is velocity?
Velocity refers to how fast a body travels in a certain direction. It is the rate of change of displacement: velocity= displacement (m)/ time (s)
What type of quantity is velocity?
Vector quantity.
What is the equation to calculate average acceleration?
Average acceleration (ms-2)= change in velocity/ time
When is momentum conserved?
Momentum being conserved occurs when a performer or object is in flight. When in flight neither mass nor velocity can be altered. Mass is constant. Velocity can only be altered by external forces (air resistance + gravity).
What is angular velocity?
Refers to the rational speed of an object and the axis about which the object is rotating. It’s a vector, it has direction as it refers to angular displacement covered in a certain time.
What is the equation to find angular velocity?
Angular velocity (rad/s)= Angular displacement (rad)/ time taken (s).
What is angular acceleration and how is it calculated?
The rate of change of angular velocity. Angular acceleration p= (rad/s2)= Change in angular velocity (rad/s)/ time taken (s).
What is Newton’s second law in relation to angular motion?
‘The rate of change of angular momentum (acceleration) a body is proportional to the force (torque) causing it and the change that takes place in the direction which the force (torque) acts.
What is Newton’s third law in relation to angular motion?
‘When a force (torque) is applied by one body to another, the second body will exert an equal and opposite force (torque) on the other body?
What are the 2 factors that the moment of inertia acting on a lever is dependant on?
- The mass of the object.
- How the mass is distributed from the point of rotation. The further the mass from the point of rotation, the bigger the moment of inertia and the harder to stop/start movement.
How does the mass of an object affect the moment of inertia?
The greater the mass, the greater the resistance to change and therefore the greater the moment of inertia. For example, a ten pin bowling ball is harder to roll along the ground than a football, but once rolling, it is more difficult to stop. Same with rotation.
How does the distribution of mass from axis of rotation affect the moment of inertia?
Closer the mass to the axis of rotation, the smaller the inertia. Thus, the easier it is to rotate. Increasing the distance of the distribution of mass from the axis of rotation will increase moment of inertia, but more rotation slower.
What is the equation to calculate angular momentum?
Angular velocity X moment of inertia
These two are inversely proportional, angular momentum is concise red so if moment of inertia increases, angular velocity decreases, visa versa.
What is the conservation of angular momentum law?
A body will keep on sprinting or rotating unless forces act upon it. A body is unlikely to lose mass during movement, but can change it’s distribution or distance from the axis of rotation.
What is equilibrium when when is it achieved?
For a body to be in equilibrium (balance) the sum of the clockwise moments is equal to the sum of the anti-clockwise moments about the fulcrum. The resistance arm must equal the effort arm.
What is Newton’s first law in terms of angular motion?
‘Every body continues in its state of rest or will turn about its axis of rotation unless compelled to change that state by an eternal rotational force (torque) acting upon it.’
