Biomechanics Flashcards
Newton’s 1st law of motion
a body continues in its state of rest of motion unless acted upon by a force
Newton’s 2nd law of motion
Rate of change of acceleration to a body is proportional to the force applied to it and inversely proportional to the mass of the object.
F=ma
Momentum
measure of the amount of motion possessed by a moving body and can be expressed mathematically as p=mv (mass x velocity)
Conservation of linear motion (COI)
Principle states the total momentum of the two objects before and after impact.
Perfectly elastic - the momentum of one object is transferred on contact to the other object, no loss of momentum.
perfectly inelastic - all moment lost
Impulse
the application of force over a period of time to change the momentum of an object
Impulse = force x time
it is a change in momentum
Newton’s 3rd law of motion
for every action, there is an equal and opposite reaction.
When two objects exert a force upon each other, the forces are opposite in direction and equal in magnitude
concept of conservation of momentum
Explains that when collisions occur, an equal and opposite force occurs resulting in a transfer of momentum from one object to the other.
coefficient of restitution (COR)
Measures the elasticity of the collision between an object and a given surface.
measures how much energy remains in the object after a collision takes place.
Measured on scale of 1-0 (1-perfectly elastic, 0-perfectly inelastic)
formula - COR=square root(height bounced/height dropped)
Factors affecting COR
Temp of ball, increase temp - increase COR
Velocity of collision, increased V - decrease COR
equipment and material
Elasticity
measure of how much rebound exists after collision
Concentric force
force applied to produce linear motion
(eg. Slapshot) - puck moves straight, hit in the middle
Eccentric force
off centre force applied to produce angular motion
(Spin on ball)
Force couples
when two equal, but oppositely directed forces act on opposite side of an axis of rotation.
This causes the forces that produce linear motion to cancel each other out, causing the object to rotate in a fixed position
angular momentum
Quantity of angular motion possessed by a rotating body and is expressed mathematically as:
angular momentum = angular velocity x moment of inertia
Moment of inertia (MOI)
refers to resistance of a rotating object to change its state of motion.
If mass of object is distributed close to the axis of rotation, the MOI is small and it is easier to rotate object. As mass of an object moves further away from the axis of rotation, the MOI increases and rotation becomes harder.
MOI=mass of object x radius of rotation
Distance of axis of rotation = radius of rotation
conservation of angular motion
Means that a spinning body will continue spinning indefinitely unless an external acts on it