Section 5: Biomechanical principles and levers Flashcards
Definition of linear motion
motion in a straight or curved line, with all body parts moving the same distance at the same speed in the same direction
What is inertia?
the resistance an object has to a change in its state of motion
State Newton’s first law of inertia
a force is required to change the state of motion
‘every body continues in its state of rest or motion unless compelled to change by external forces exerted upon it’
State Newton’s second law of acceleration
the magnitude and direction of the force determines the magnitude and direction of acceleration
‘the rate of momentum of a body is proportional to the force causing it and the change that takes place in the direction in which the force acts
State Newton’s third law of motion
for every action there is an equal and opposite reaction
What is ground reaction force?
the equal and opposite force exerted on a performer who applies a muscular force on the ground
What is the centre of mass?
the point of balance
What is the line of gravity?
the line extending vertically downwards from the centre of mass
What factors affect stability?
- the height of the centre of mass
- position of the line of gravity
- area of the support base
- mass of the performer
What 3 components make up a lever system?
-fulcrum, effort, load
Explain each component of a lever system
fulcrum= the point about which a lever rotates resistance= the weight to be moved by the lever system effort= the force applied by the user (muscle) of the lever system
What is a first class lever?
The fulcrum lies between the effort and resistance
123,FLE
What is a second class lever?
The resistance/load is in between the fulcrum and effort
What is a third class lever?
The effort is in between the fulcrum and resitance
What are force and resistance arms?
Force arm= the length of the line between where the fulcrum and effort are labelled
Resistance arm= the length of the line between where the fulcrum and resistance are labelled
What is a mechanical advantage?
Where the force arm is longer than the resistance arm
What is a mechanical disadvantage?
Where the resistance arm is longer than the force arm
Which type of lever has a mechanical advantage?
2nd class
-generates large amounts of force e.g. pushing up on your toes
Which type of lever has a mechanical disadvantage?
1st and 3rd class
-can’t apply lots of force e.g. triceps extension of the elbow and bicep flexion
Give an example of Newton’s first law/law of inertia
a ball remains at rest until it is hit, thrown or kicked. tackling a rugby player that is bigger than you, they won’t move because they have a larger inertia
Give an example for Newton’s second law/law of acceleration
the harder you kick a ball in one direction the further it will travel in that same direction
Example of Newton’s third law (action/reaction)
a sprinter pushes back on the blocks (action) and the blocks push the athlete forwards (reaction) which provides the athlete with acceleration- called ground reaction force
What is an example where factors affecting the centre of mass are used in sport?
a sprinter at the start keeps the line of gravity over the base of support at the on your marks. Then as the set is called they move this forward to the edge of the base. This means that on the gun as their hands move away they will fall forward into a running position
Give an alternative example where factors affecting the centre of mass are used in sport?
a rugby player going into contact keeps their centre of mass and therefore bodyweight low so that they are harder to move
Examples of first class levers
- lifting your head off you chest
- tricep extension over your head
Example of a second class lever
-pushing up on your toes e.g. in ballet
Examples of third class levers
- bicep curl
- kicking a ball
