Linear Kinetics 1 Flashcards
Projectile motion ^ vertical velocity = ?
^ Height, flight time, range
Projectile motion ^ horizontal velocity = ?
^ range
same height, flight time
Shot put optimal release angle and why
38-43 degrees because release height > landing height
Long jump maximum range (L1-3) explained
L1 & L3 = body position (take off/landing)
L2 (flight time) = velocity at take off
Long jump optimal release angle and why
15-22 degrees because centre of mass higher at take off than landing
Inertia definition
the resistance of a body to motion
Mass definition
amount of matter in a body (kg)
^ mass = ^ inertia
Force defintion
Causes motion (N - newtons)
Alters a body’s state of rest/uniform motion
1N = 1kg mass accelerated by 1m/s/s
Force explained
Force is a vector (mag + direction)
Point of application is important can be contact (eg in a joint) and non contact forces (gravity)
Newtons law of gravitation explained
Any 2 particles attract one another with directly proportion force to the product of their masses and inversely proportional to the square distance between them
F = m1m2 / d^2
Weight definition
Weight is attractive (gravitational) force that exerts on a body
Weight varies on location mass is constant
Newtons first law of motion explained
Every body is in a state of rest or uniform motion in a straight line unless compelled to change by external forces acting on it
Newtons second law of motion explained
Acceleration of a body is proportional to the force causing it and the change follows the direction the force acts
F = ma
Mass - Weight relationship example
Divers mass = 55kg
Force = weight (W)
f = ma = W = 55x -9.81 m/s = -539.6 N
Newtons 3rd law of motion explained
For every force that is exerted there is an equal and opposite force going the other way (action & reaction)
How are ground reaction forces (GRF) measured
Force plates
What does the force plate measure
Vertical GRF
Anterior-posterior GRF
Medial-lateral GRF
Vertical GRF graph explained
First peak = peak impact force
Second peak = peak active force
(for rear foot strikers)
1500N ish
Horizontal GRF (anterior-posterior) graph explained
Negative initial phase (breaking phase) because the force is applied forwards (so reaction is backwards) - peak breaking force
Second positive phase is when the runner is pushing off so reaction force is forwards - peak propulsive force
300N ish
Vertical GRF for walking
Double peak shaped curve
Longer contact time
less force produced (900N)
Horizontal GRF for walking
same shape graph but less magnitude (force)
Factors influencing GRF
Speed
Mass
Surface?
gait kinematics?
footwear?
