Biomechanical Principles, external factors and free body diagrams Flashcards
What are Newton’s three laws
1st law - law of inertia
2nd law - law of acceleration
3rd law - law of reaction
Define Newton’s first law of inertia
A body will remain in a state of rest or uniform velocity unless acted on by an external or unbalanced force
Define Newton’s second law of acceleration
The acceleration of a body is proportional to the size of the force applied and takes place in the direction at which the force acts
Define Newton’s third law of reaction
For every action there is an equal and opposite reaction. The reaction force is equal in size and opposite in direction to the action force
Give a sporting example of Newton’s first law of inertia
A football will remain at rest on the penalty spot until a force is applied to the ball by the players foot
Give a sporting example of Newton’s second law of acceleration
The acceleration of a netball during a pass is proportional to the force from the muscle and is in the same direction of the force
Name a sporting example of Newton’s third law of reaction
When serving, a tennis player pushes downwards on the ground (action force) and the ground pushes upward on the player (reaction force)
Define force
Force is a push or pull that tends to alter the state of motion of the body
Define balanced forces
When two or more forces acting on the body are equal in size and in opposite directions they cancel out
Define unbalanced force
When two or more forces acting on the body do not cancel out so a net force acts upon the body
Define net force
Also known as the resultant force, this is the overall force acting on a body when all forces are considered
Where do external forces originate from
Outside the body
What are the 4 external forces
Weight, reaction, friction and air resistance
Define weight
The force that acts directly downwards from the centre of mass
Define reaction
Reaction force acts upwards from the point(s) of contact with the ground in reaction to all forces
Define friction
Friction opposes the sliding motion of one surface across another
Define air resistance
Air resistance acts against the direction of motion opposing the movement of the body through the air
What are the 4 factors effecting friction
- Characteristics/roughness of surface 1 (sole of footwear)
- Characteristics/roughness of surface 2 (playing surface)
- Force/normal ground reaction force (the force pushing the two surfaces together)
- Temperature (heated tyres increase friction)
State 3 ways in which friction can be maximised
- Increase the roughness of surfaces
- Increase the mass/downforce (heavy props)
- Increase the temperature of materials
State one way in which you can minimise friction
Increase the smoothness of surfaces
State the 4 factors that effect air resistance
- Velocity of person/object
- Frontal cross section of object
- Streamline/shape of object
- Surface characteristics
State three ways in which air resistance can be minimised
- Reduce the frontal cross sectional area
- Using a streamline shape
- Making surfaces smoother
Where does weight originate from
Centre of mass
Which direction does weight act upon
Vertically downwards
How long is the arrow for weight
Proportional to the objects mass
Where does reaction originate from
All points of contact with the ground
Which direction do reaction forces act
Upwards perpendicular to the ground
How long are the arrows representing reaction
Equal but opposite to all downwards acting forces
Where does air resistance originate from
Centre of mass
Which direction does air resistance act
Opposite to the direction of motion
How long is the arrow representing air resistance
Proportional to velocity and other factors effecting air resistance
Where does friction originate from
All points of contact with the ground
Which direction does friction act
In the direction of motion
How long are the arrow representing friction
Proportional to the factors effecting friction
