U3AoS1 - Biomechanical Principles Flashcards
Biomechanical Principles
Study of human movement and the forces acting upon it, both internal and external. During both motion and stationary.
Mass
Is the quantity of matter found within a particular body/object
Inertia
The tendency for an object to resist a change in its state of motion.
Relationship between mass and inertia
The greater the mass, the greater the inertia.
Force
Can be described as a push or pull on an object.
Mass x Acceleration
Internal and External
Force applied needs to be greater than the inertia for movement.
The effects of Force on an object
- Change the shape of an object
- Change an objects speed/motion (acceleration, negative acceleration)
- Change an objects direction
Torque
Force around an axis
Internal Force
Muscles pulling on bones at a joint
External forces
Air and water resistance, friction and gravitational forces.
Air and water resistance
A frictional force that occurs when one of the surfaces is air or water (drag force)
Friction
Occurs when two surfaces contact each other. Friction can be manipulated to be increased or decreased.
E.g. Curling, soccer and golf
Gravitational Forces
Constant downward force acting at 9.8m/s^2
Gravity effect on ball flight path
Force of gravity brings ball back to earth in a parabolic path.
Motion
Refers to the change in position of an object/body in relation to time. Something moving.
Types of Motion
- Angular Motion
- Linear Motion
- General Motion
Acceleration description
An object positively changing motion
Deceleration
Something decreasing motion
Velocity
Speed with a direction
Linear Motion
Something moving in a straight line or curved path. All parts travel the same distance in the same direction and time.
Angular Motion
When a body part moves around a central axis/twisting or rotates around an axis.
Axis is stationary.
General Motion
Linear and Angular Motion
eg. cycling and running
If acceleration is 0
The speed is constant and unchanging
Newtons Laws
- Inertia
-Force and Acceleration - Action and Reaction - Rarely used in Isolation
Newtons First Law
An object will stay at rest or continue to travel in the same direction at a constant velocity unless acted upon by an external force.
- If an object is at rest, it will remain at rest. If the object is in motion, it will tend to remain in motion.
Newtons first law referring to mass.
The greater the mass, the greater the inertia. More force is therefore required to change motion.
Newtons Second Law
The rate of acceleration of an object is proportional to the force applied to it and in the direction in which the force is applied
- If mass stays the same, the greater the force = the greater the acceleration
- An object will accelerate faster when a greater force is applied.
In order to generate maximal force
Mass and acceleration should be highest.
However, there is a trade off between mass and acceleration - pyshiological struggle.
If the amount of force produced by a body is equivalent
Then the object with more mass will not accelerate as quickly.
Newtons Third Law
When two objects come into contact with one another, they exert equal forces that are equal in size but opposite in direction to one another.
- For every action, there is an equal and opposite reaction.
Newtons Third Law in an answer
Must state
- action force
- reactive force
- equal and opposite force
- performance benefit.
Momentum
A measure of the amount of motion an object has and its resistance to changing that motion.
Types of momentum
Linear momentum and angular momentum
Linear Momentum formula
Mass x Velocity
Angular Momentum formula
Moment of inertia x angular velocity
Moment of inertia
The resistance of a body to change its angular momentum.
Can be manipulated by shifting body parts.
Angular velocity
Rate of rotation around and axis (RPM) . MOI must be changed to change AV.
Linear Momentum
Zero velocity = zero momentum
If two objects have the same mass, the object with the greater velocity will have greater momentum.
Greater the momentum = harder to stop
Conservation of linear momentum
States that when two objects come into contact, the total momentum that existed before the collision is the same as the total momentum after.
Transfer of momentum based on which object has the greater mass/velocity.
All momentum
is conserved.
Decreased moment of Inertia
Bring mass closer to rotation axis will increase angular velocity
Increased moment of inertia
Take mass away from the axis will decrease angular velocity
Conservation of Angular Momentum
Once a force is applied, angular momentum is conserved (mass will not change). Only angular velocity can be changed by changing MOI.
Summation of momentum
Use large muscles first, each body part then sequentially accelerated, each body part stabilized before momentum transferred.
Why do we use large muscles first?
Such as thighs and trunk, these have high mass and hence move more slowly. Large body parts initiate the movement and provide the base for support.
Sequentially accelerated
Momentum from large and slow, to small light and fast body parts.
Why do we use Summation of momentum?
- By using as many body parts as possible of possible, the time over which the force is applied is maximized.
- Follow through is important so the last body part doesn’t slow down.
Impulse
Force x time = change in momentum.
Impulse reasoning
Applying force for longer results in a change of momentum. Impulse can be applied to an object to either increase or decrease momentum.
Injury prevention
Absorbing force over time will decrease the momentum
Using no mat
Will result in a larger impact force as the force is absorbed in a short period of time.
Using a mat
Crash mats aborbs the force over a longer period of time, less risk of injury due to smaller impact force.
Cricket ball example
Moving your hands back will increase the amount of time over which the force is applied to your hands, decreasing the impulse.
Projectile
any object that is launched into the air becomes a projectile.
- affected by air resistance and gravity
Concerned with the vertical, horizonal or a combination distance.
Factors affecting path and distance of a projectile.
Speed of Release (2nd Law)
Angle of Release
Height of Release
Speed of Release
- The greater the force applied, the greater the acceleration
- Increasing the speed of release = further and faster travel
Acceleration formula
Force/mass
Angle of Release
The optimal angle of release to travel the greatest distance is 45 degrees.
Height of Release
If the angle and speed of release are constant, an object released from a greater height will travel further.
Relative projectile height = 0
45 degree release angle
eg. Golf and Soccer
Relative projectile height = 2m
<45 degree angle
eg. Cricket and bowling
Relative projectile height = -1.5m
> 45 degree angle
eg. Netball and Basketball
Stability and Balance can be manipulated by:
- Base of Support
- Mass
- Line of Gravity
- Centre of Gravity
Stability and Balance can be improved by:
- Lowering center of gravity
- widening base of support
3. Ensure line of gravity is in the middle of base of support.
Levers
Simple machine consisting of a rigid bar that can be made to rotate around in axis to exert force.
Bones = Rigid bar
Joints = axis
Force = Muscles contract
Axis
AKA Fulcrum
The turning point of the lever
Force (Levers)
AKA Effort
- the point where force is applied
Resistance
AKA Load
The weight being moved
ARF Acronym
RAF = 1st class
ARF = 2nd class
AFR = 3rd class
1st and 2nd Class Levers
Role = Decreasing the amount of force required to move a mass.
No first class levers in the body
- 2nd class lever = calf raise.
Force arm
The distance between the axis and the force
Resistance arm
Distance between the load and the fulcrum.
3rd Class Levers
Role = increase the speed and range of movement at the end of the lever.
Benefit of increasing the Resistance arm
Increasing the resistance arm = increased range of motion and therefore speed.
Allows for increased linear velocity to be transferred to objects resulting in increased distance.
Mechanical advantage
If resistance arm is longer than the force arm = less than one (which more force is required to move the object) as they increase the speed of the lever not the force.
Running example referring to inertia
Decreasing the moment of inertia and resistance arm enables the leg to be swung through more quickly, greater angular velocity.
Displacement
Straight line path travelled between two points including direction
Distance
Total length of path travelled between two points
Speed
Time taken to cover a certain distance
distance/time
Velocity
Speed with a direction
displacement/time
Acceleration formula
Change in velocity over a period of time
velocity/time.
Weight
The force that gravitation exerts upon a body, equal to the mass of the body x gravity force.
Equilibrium
No acceleration of body (no change of speed + direction)
Centre of Gravity
The average location of all the weight of an object
Stability
Resistance to a disruption of equilibrium.
Line of gravity
Imaginary vertical line passing from the centre of gravity of an object to the ground
Base of Support
The area beneath a person that includes every point of contact with a surface
Linear Velocity
How quickly something is changing motion in a straight line or curved path.
