5. Biomechanical Principles And Levers Flashcards
What are Newtons 3 laws?
- The law of inertia
- The law of acceleration
- The law of action/reaction
Define ‘newtons first law of inertia’
A force is required to change the state of motion
Define inertia
The resistance an object has to a change in its state of motion
Key points of Newton’s first law
- if an object is at rest, it will remain still
- if an object is moving in one direction it will continue to do so at the same velocity until another force is exterted upon it.
- the bigger the mass, the larger the inertia of an object
Sporting example for Newton’s first law
In a penalty, the ball will remain on the spot (state of rest) unless it is kicked by the player (external force).
Define ‘newtons second law of acceleration’
The magnitude (size) and direction of the force determines the magnitude and direction of the acceleration.
Key points of Newton’s second law
- the rate of acceleration is directly proportional to the force causing the change
What is the equation in Newton’s second law
Force = mass x acceleration (F = ma)
Sporting example for Newton’s second law
The harder the ball is kicked, the further and faster it will go in the direction that the force has been applied in.
Define ‘newtons third law of motion’
For every action (force) there is an equal and opposite reaction (force)
Key points of Newton’s third law
- always occur in pairs
Define ‘ground reaction force’
The equal and opposite force exerted on a performer who applies a muscular force on the ground.
Sporting example for Newton’s third law
When a footballer jumps (action) to win a header, a force is exerted on the ground to gain height. At the same time, the ground exerts an upward force on the player.
Define ‘scalar quantity’
When measurements are described in terms of just their size or magnitude.
How do you calculate speed?
Distance (m) / time (s)
Define centre of mass
The point of balance
Define line of gravity
The line extending vertically downwards from the centre of mass
What principles should be considered to increase stability?
- height of the centre of mass: lowering this will increase stability
- position of the line of gravity: should be central over the base of support to increase stability
- area of the support base: more contact points = bigger base
- mass of performer: greater mass = more stability due to increased inertia
Define ‘area of support base’
The larger the area, the greater the stability
Define fulcrum
The point about which the lever rotates
Define resistance
The weight to be moved by the lever system
Define effort
The force applied by the user (muscle) of the lever system
Define first class lever
The fulcrum lies between the effort and resistance
Define second class lever
The resistance is between the fulcrum and effort
Define third class lever
The effort is between the fulcrum and the resistance
Sporting example of first class lever
Extension of the elbow
Sporting example of second class lever
Planter flexion of the ankle
Sporting example of third class lever
Hip, knee and elbow flexion
Define force arm
The length of the line between where the fulcrum and effort are labelled
Define resistance arm
The length of the line between where the fulcrum and the resistance are labelled.
What is a mechanical advantage and disadvantage?
Where the force arm is longer than the resistance arm
Where the resistance arm is longer than the force arm
What is the mechanical advantage/disadvantage of a second class lever?
Can generate much larger forces
Slow with a limited range of movement
What is the mechanical advantage/disadvantage for a first and third class levers?
Large range of movement and any resistance can be moved quickly.
Cannot apply much force to move an object
Define 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
