11. Biomechanics Flashcards
Force definition
A push or pull that alters the state of motion of a body
What can a force do to a body?
Change direction
Accelerate
Decelerate
Change shape
Force formula
Force (N) = mass (kg) x acceleration (m/s2)
Examples of internal forces
Concentric muscle contraction
Examples of external forces
Gravity
Air/water resistance
Friction
Reaction - ground reaction force (GRF)
What is linear motion?
Motion in a straight or curved line with all body parts moving same distance, speed & direction
Eg. Tobogganing, toboggan moves in a straight line
What is angular motion?
Movement around a fixed point or axis - suggests movement is circular or rotational
Eg. Somersault
What is general motion?
Movements that are a combination of linear & angular motion
Eg. Run up in javelin - body moves in a straight line, throwing action in circular
Inertia definition
Reluctance of an object to change its state of motion
↑ mass =↑ inertia
Newton’s 1st law of motion
Law of inertia
An object at rest stays at rest, an object in motion stays in motion unless acted upon by external forces
Eg football won’t move until it is kicked, will move in straight line until kicked again
Newton’s 2nd law of motion
Law of acceleration
F = ma
A force acting on an object is equal to its mass x acceleration
The rate of change of momentum of a body is directly proportional to its force causing it
Eg during a penalty kick, if a player applies force to a ball it will move in the direction the force is applied
Newton’s 3rd law of motion
Law of action & reaction
For every action here is an equal & opposite reaction
E.g. When jumping a a springboard, the springs compress then bounce back up
Momentum concept
Allows us to understand how mass & velocity influence the movement of an athlete or object
Impulse concept
Allows us to explain now force & time can cause an athlete to start moving or change direction
M momentum definition
The quantity of motion
Momentum formula
Mass (kg) x velocity (m/s) = momentum (kg m/s)
Velocity definition
The speed something moves in a given direction
Impulse definition
The product of force & the time it takes to apply the force
Impulse = change in momentum
Impulse formula
Force (N) x time (s) = impulse (Ns)
How is impulse represented?
The area under a force-time graph
Can be classified as positive or negative
Net impulse definition
The overall change in momentum of an object
It takes into account both positive & negative impulses
Net impulse formula
Net impulse = positive impulse - negative impulse
Positive impulse example
Larger positive impulse than negative impulse
Eg athlete pushing off ground, accelerating forwards
Force applied by a bat striking the ball
Occurs when force is applied in same direction as the motion of an object, increasing its velocity
Negative impulse example
Larger negative impulse than positive impulse
Eg performer is decelerating
Occurs when force is applied in the opposite direction to the motion of the object, decreasing its velocity
How does impulse change momentum?
The larger the force or the longer it acts for the more momentum changes
How can a performer increase impulse?
- Increase force applied
- Increase time the force is applied for
- Increase both force & time
Stability definition
The ability of a body to return to equilibrium after being displaced
Centre of mass definition
The point at which the body is balanced in all directions
Line of gravity
Line which passes vertically from centre of gravity to the ground below object
What is stable equilibrium?
A state where a system remains unchanged & can return to its original state after disturbance
Factors that affect stability
- mass of object
- Size of base of support
- Height of centre of mass
- Points of contact with surface
