Biomechanics Flashcards
Newton’s 1st law
-The law of Inertia
When a body continues in a state of rest or moving with constant velocity in a straight line, unless acted upon by an external force
Newton’s 2nd Law
-Law of attraction
- When a force acts upon an object, the rate of change in momentum experienced by the object is proportional to the size of the force and takes place in the direction in which the force acts
- Greater force= greater acceleration
Newton’s 3rd Law
-Law of action/reaction
For every action, there is an equal and opposite reaction
Linear motion
Movement of a body in a straight or curved line, where all parts are moving the same distance, in the same direction, over the same time
Angular motion
Movement of a body or body part in a circular path about an axis of rotation
General motion
- Is a combination of linear and angular motion
- The trunk moves in a linear motion (straight line) as a result of other body parts (arms and legs) moving in angular motion at the shoulder and hip joint
Force applied outside of the COM is known as…
Eccentric, which gives us angular motion
Force applied through the COM is known as…
Direct force, which gives us linear motion
Velocity definition
The rate of change in displacement
Velocity equation
Velocity (m/s)= Displacement(m) / time taken(s)
Acceleration definition
The rate of change in velocity
Acceleration equation
Acceleration (m/s/s)= (final velocity-initial velocity) / time taken
Momentum definition
The quantity of motion possessed by a moving body
Momentum equation
Momentum (kgm/s)=mass x velocity
Centre of mass definition
The point where the mass of the body tends to be concentrated and balanced in all directions
Centre of mass depends on…
- The body’s position
- The athlete’s body itself (shape)
- Gender
Stability definition
A stable body position will enable an athlete to resist motion
The stability of an athlete is determined/affected by…
- The mass of the body
- Size of the base of support
- Height of the centre of mass
- No. of pointes in contact with the surface
- Proximity of the line of gravity to the centre of the base of support
Line of gravity
An imaginary line which extends from the COM directly to the ground
How to increase stability…
- Increase mass of the body/object
- Increase the size of the base of support
- Lower the centre of mass
- Increase the number of points in contact with the surface
- Bring the line of gravity inside the base of support
Force definition
- A push or a pull that alters the state of motion of a a body
- Measured in Newtons (N)
Force equation
Force (N) = mass x acceleration
What can force do?
- Create motion
- Accelerate/ decelerate a body
- Change the direction of a body
- Change the shape of a body
Net force
The overall force acting on a body when all individual forces have been considered
Balanced force
When two or more forces acting on a body are equal in size (Net force is zero)
Unbalanced force
When forces acting on a body are unequal in size (resulting in net force)
Vertical forces
-Weight and reaction force
Horizontal forces
-Friction and air resistance
Weight definition
Gravitational force that the Earth exerts on the body (downwards)
Reaction definition
Whenever there is a point of contact between 2 bodies, there will always be a reactionary force
Air resistance definition
The air that acts upon the body moving through the air
Friction definition
The force that acts in opposition to the movement between two surfaces in contact
Types of friction
-Sliding friction
Occurs when two surfaces have a tendency to slide over one another
Types of friction
-Direction friction
Friction acts in the opposite direction to motion
Types of friction
-Parallel friction
Friction acts parallel to the two surfaces in contact with each other
Factors affecting friction
- Roughness/smoothness of footwear in contact with the ground
- Roughness/smoothness of ground or court
- Size of the down force
- Temperature of the surface
Factors affecting air resistance
- Shape of object
- Speed/velocity
- Frontal cross-sectional area
- Smoothness of surface
Fulcrum
Fixed point of rotation about which the lever moves
Load
The resistance or weight to be moved
Effort
- The force being applied that causes the lever to move
- The agonist muscle in the human body
Load arm
The perpendicular distance from the fulcrum to the load
Effort arm
The perpendicular distance from the fulcrum to the effort
Draw the 1st class lever
Draw the 2nd class lever
Draw the 2nd class lever
Draw the 3rd class lever
Efficiency of the lever systems
- The greater the distance of the effort or load from the fulcrum, the more significant the effort or load becomes
- Longer levers generate more force
Mechanical advantage
- 2nd class levers have a mechanical advantage as the load lies between the effort arm and the fulcrum
- A small amount of effort is needed to move a large load
Mechanical disadvantage
- 3rd class levers have a mechanical disadvantage as the effort lies between the fulcrum and the load
- The lever will struggle to move heavy loads in this manner
Limb kinematics
- The study of motion, limbs and movement
- They measure movement efficiency, gait and velocity
- Used in golf and football
- Strengths: Helps to improve technique and avoid injury
- Weakness: Results do not cater for individual differences
Wind tunnels
- Large tubes with air moving inside them
- They measure aerodynamic efficiency
- Used in F1 and cycling
- Strengths: Control environmental variables and is quick and efficient
- Weakness: Very expensive
Force plates
- Rectangular metal plates, used in combination with video analysis
- Measure velocity-time, force, acceleration etc.
- Used in swimming (starts and turns) and long jump
- Strength: Injury prevention and immediate data collection
- Weakness: Not available to most
