3.1 - Biomechanical principles: Newton's laws of motion, force and use of technology Flashcards
biomechanics definition
study of human movement and the effect of force and motion on sport performance
biomechanics allows coaches to:
- analyse performance
- maximise movement efficiency and sport technique
- reduce and prevent injuries
- design and choose correct equipment to satisfy demands of activity
newtons 1st law of motion definition + application
body continues to stay in a state of rest or uniform velocity unless acted upon by an external or unbalanced force
- 100m sprinter remains at rest in blocks until internal force large enough to overcome their inertia creates motion
newtons second law motion definition + application
- body’s rate of change in momentum is proportional to the size of the force applied and acts in the same direction as the force applied
- greater force applied to sprinter = greater rate of change in momentum = greater acceleration
newtons third law of motion + application
for every action force applied to a body, there is an equal and opposite reaction force
- when sprinter applies down and backward action to blocks, blocks provide an equal up and forward force.
velocity formula
displacement/time taken
momentum formula
mass x velocity
kgm/s
acceleration formula
final velocity - initial velocity/ time taken
force formula
mass x acceleration
two types of force
internal force - generated by contraction of skeletal muscle, eg 100m sprinter contracting rectus femurs to extend knee
external force - comes from outside the body and acts upon it, eg, air resistance, weight, friction
what does it mean when resultant forces are not = 0
body will accelerate/decelerate, etc
weight formula
mass x acceleration due to gravity(9.81N on earth)
w = r1+ r2
what is a reaction force?
the equal and opposite force exerted by a body in response to the action force placed upon it
what four factors is air resistance affected by?
- velocity
- shape
- frontal cross sectional area
- smoothness of the surface
how do high jumpers maximise reaction force?
- lean back to extend time action force is applied to the track
- arm swings and leg extends (internal force)
limb kinematics definition + adv/disadv
3d or optical motion analysis records an athlete performing a sporting action
- accurate, immediate and objective
- coach use to improve technique such as football kick
- depends on correct placement of bodily markers
- expensive and limited to lab conditions
force plates definition + adv/disadv
- rectangular plate that measures force applied
- immediate, accurate and reliable results can be used to analyse performance
- specialist, expensive and limited to lab conditions
wind tunnels
allow measurement of wind, can change wind velocities to help decide how to streamline an object for maximal performance
- Time efficient
- Can see force and direction of wind
- Specialised facilities
- Expensive and require complex analysis of results by research professionals
Zero net force
means acceleration is zero, or object at rest, eg rugby scrum pushing at same force, so no movement
Forces
- create motion
- Accelerate a body
- Decelerate a body
- Change direction of a body
- Change shape of a body
Friction affected by:
- roughness of ground surface
- Roughness if contact surface (sprinters spikes)
- Temperature - higher = more
- Size of normal reaction
Weight + reaction force
Weight - from centre of mass extending vertically downwards
Reaction force - from point of contact extending vertically upwards
If r>w, eg basketballer take off phase - net force is positive = acceleration in upward direction
Friction
from point of contact and usually extending horizontally in the same direction as motion
Air resistance
from the centre of mass and extending horizontally against the direction of motion
