Biomechanics (Y1+2) Flashcards
Define Newton’s 1st Law
A body continues in a state of rest or moving with constant velocity in a straight line, unless acted upon by an external force.
Define Newton’s 2nd Law
When a force acts on an object, the rate of change of momentum experienced by the object is proportional to the size of the force and takes place in the direction in which the force acts.
Define Newton’s 3rd Law
For every action, there is an equal and opposite reaction.
Define Velocity
The rate of change in displacement
How do you calculate velocity?
Velocity (m/s) = Displacement (m)/Time taken (s)
Define Momentum
The quantity of motion possessed by a moving body
How do you calculate momentum?
Momentum (kg m/s) = mass (kg) x velocity (m/s)
Define Acceleration
The rate of change of velocity
How do you calculate acceleration?
Acceleration (m/s/s) = Final velocity - initial velocity / time taken
How do you define centre of mass?
The point where the mass of the body tends to be concentrated and balanced in all directions
What factors affect stability?
- The mass of the body
- Size of the base of support
- Height of the centre of mass
- No. of points in contact with the surface
- Proximity of the line of gravity to the centre of the base of support
What is the line of gravity?
An imaginary line which extends from the centre of mass directly to the ground
How can you increase stability?
- Increase mass of the body/ object
- Increase the size of the base of support
- Lower of the centre of mass
- Increase the number of points in contact with the surface
- Bring the line of gravity inside the base of support
How do you calculate force?
Force (N) = Mass x Acceleration (F=Ma)
Define Force
A push or pull that alters the state of motion of a body. (N)
What is Net Force?
The overall force acting on a body when all individual
forces have been considered
What is a balanced force?
Balanced Forces: When two or more forces acting on a body are equal in size but opposite in direction. – Net Force is ZERO.
What is an unbalanced force?
When force acting in one direction on a body is greater in size than force acting in the opposite direction. – Resulting in Net Force
Name two vertical forces?
Weight & Reaction Force
Name two horizontal forces?
Friction & Air Resistance
Define friction
The force that opposes the motion of two surfaces in contact. (N)
Identify 4 factors that impact upon friction
Roughness or smoothness of footwear or object in contact with the ground.
Roughness or smoothness of the ground or court.
Size of the down force
Temperature of Surface
Identify 4 factors that impact upon air resistance
- Shape of object
- Speed/velocity of release
- Frontal cross sectional area
- Smoothness of surface
What are the 3 components of a lever?
Fulcrum, Effort, Load
What is the fulcrum?
Fixed point of rotation about which the lever moves.
What is the load?
The resistance or weight to be moved. The weight of a human body part to be moved is the load.
What is the effort?
The force being applied that causes the lever to move. The agonist muscle in the human body.
What is the load arm?
The perpendicular distance from the fulcrum to the load.
What is the effort arm?
The perpendicular distance from the fulcrum to the effort.
What is the tip to remember the class of lever?
1-2-3 F-L-E. A lever is classified by which component is in the middle of the other two components.
Give 2 examples of a 1st class lever.
The head (atlas joint) & triceps brachii (elbow joint)
Give an example of a 2nd class lever
The ankle (phalanges & metatarsals)
Give an example of a 3rd class lever.
Biceps brachii (elbow joint)
Which levers generate more force? Long or short?
Long
Which lever has a mechanical advantage?
2nd class due to the greater length of the effort arm in comparison to the load arm
What can force plates measure?
Force-Time
Acceleration-Time
Velocity-Time
Displacement-Time
Force-Displacement
Motion-Gait
Impulse
What is linear motion?
Linear motion is movement of a body in a straight or curved line, where all parts move the same distance, in the same direction, over the same time.
How is linear motion created?
Linear motion results from a direct force being applied to a body, directly to the centre of mass.
Define distance
The total length of the path/ route covered from start to finish (not necessarily straight line)
Define displacement
The shortest straight-line route from start to finish
Define speed
The rate of change in distance (m/s)
What is deceleration?
When the rate of change of velocity is negative or there is a decrease in velocity over time
What is angular motion?
Angular motion results from an eccentric force being applied to a body, OUTSIDE of the centre of mass (known as torque)
Name the three axis of rotation.
Longitudinal, Transverse, Frontal.
What is angular motion measured in?
Radians - rad/s
What are the three components of angular motion?
Angular Velocity, Moment of Inertia, Angular Momentum.
How do you calculate Angular Momentum?
Angular Momentum = Angular Velocity x Moment of Inertia
Define Angular Momentum
The quantity of ANGULAR motion possessed by a moving body (kgm2)
Define Angular Velocity
The rate of change in angular displacement OR
the rate of rotation (rad/s)
How do you calculate Angular Velocity?
Angular velocity (rad/s) = angular displacement (rad)/time taken (s)
Define Moment of Inertia (MI)
Moment of Inertia is the resistance of a body to change its state of angular motion or rotation (kgm2)
How do you calculate Moment of Inertia (MI)?
Moment of Inertia (kgm2) = Sum of (∑)
(Mass (kg) x Distribution of Mass from Axis of Rotation(m2))
MI = ∑m x r2
REMEMBER YOU ONLY NEED TO LEARN THIS EQUATION
What are the two factors affecting Moment of Inertia?
Mass & Distribution from the Axis of Rotation
How do you generate angular momentum?
Applying Torque - Applying an eccentric force (outside the axis of rotation)
What is the Conservation of Angular Momentum?
A rotating body will continue to turn about its axis of rotation with constant angular momentum unless acted upon by an eccentric force or external torque.
Once angular momentum has been generated, what happens if MI increases?
Angular velocity decreases
Once angular momentum has been generated, what happens if MI decreases?
Angular velocity increases
How does air resistance differ to drag?
Drag is the fluid resistance encountered in water
What is projectile motion?
The movement of a body through the air following a curved flight path under the force of gravity
Horizontal distance following projectile motion is affected by 4 factors. Name them.
Speed of release
Angle of release
Height of release
Aerodynamics (Bernoulli & Magnus)
What is the optimal angle to maximise horizontal distance if release height and landing height are equal?
45 degrees
What is a positive release height?
If the release height is above the landing height.
What is a negative release height?
If the release height is below the landing height.
If there is a negative release height, what happens to the optimum angle of release?
It increases above 45 degrees.
What is a parabolic flight path?
When a projectile is unaffected by air resistance and follows a uniform curve, symmetrical at it’s highest point.
When will a projectile have a parabolic flight path?
When weight is the dominant force (eg. shot put).
What is a non-parabolic flight path?
When a projectile is affected by air resistance. The flight path is therefore asymmetrical about its highest point as a result (Eg. shuttlecock).
On a free body diagram for a projectile, which 3 labels should be shown?
Direction of motion/Air Resistance/Weight
On a resultant forces parallelogram, which 4 labels should be shown?
Direction of motion/Air Resistance/Weight/RESULTANT FORCE
Using a resultant force label on a resultant forces parallelogram, how do you determine the dominant force?
The line the resultant force arrow is closest to shows the result force (either Air Resistance or Weight)
What is the Bernoulli Principle?
An additional force can be created by a pressure gradient as a result of differing air velocities.
If air moves at high velocity is the air pressure high or low?
LOW
If air moves at low velocity is the air pressure high or low?
HIGH
What ‘A’ is the name of the object that is required to apply the Bernoulli Principle in sport.
Aerofoil
What is the optimal ‘angle of attack’ when attempting to create an aerofoil eg. when throwing a discus?
17 degrees
What do you need, to create downward force through the Bernoulli principle?
An inverted aerofoil
Does the air travel at a greater velocity over the top or underneath a formula 1 car?
Underneath
What two parts of a formula 1 car, funnel the air at a high velocity underneath the car?
Front wing & spoiler
Is the air pressure greater underneath or on the top of a formula 1 car?
On the top
What is the magnus effect?
Applying spin, eccentric force outside the COM (magnus force), to a projectile will create greater air resistance in a particular direction. This decreases air velocity, increasing pressure on this side.
When air flows lines are wider, do the show higher or lower air pressure?
HIGHER
When air flow lines are narrower, do they show higher or lower air pressure?
LOWER
When air flow lines are wider, is air velocity high or low?
LOW
When air flow lines are narrower, is air velocity high or low?
HIGH
What 6 labels must be on a magnus force diagram that shows the impact of the magnus effect on a projectile?
Air flow lines (wide & narrow), application of force, the projectile, direction of spin, direction of swerve, direction of movement.
