6834 Lecture Notes - Lecture 4: Ground Reaction Force, Potential Energy, Kinetic Energy
Lecture 4
Forces and linear kinetics
- Force
oAn interaction that causes a change in motion of an object
oForce is a vector (has magnitude and direction)
oInternal – muscle/bone
Tensile/compressive/shear forces
oExternal
Gravity (-9.81m/s)
Impacts weight as it is mass x gravity
Contact: once we start hitting objects
- Ground reaction force – only vertical
o
find more resources at oneclass.com
find more resources at oneclass.com
o
Force over time
These two are the same
Acceleration and force are the same
Numbers will be different
Impart most forces in deepest level ie bottom of squat
oNet force (resultant)
Ultimate direction and magnitude
Co-linear forces
Forces acting in the same direction
Concurrent forces
oIf one is bigger - movement
oFree body diagrams
Take pictures; use arrows to describe where you think forces are
oStatic analysis
Equilibrium
Sum of all forces on body = 0
If not 0 = unbalanced = movement
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Force: an interaction that causes a change in motion of an object, force is a vector (has magnitude and direction, internal muscle/bone. Impacts weight as it is mass x gravity. Ground reaction force only vertical o o. Impart most forces in deepest level ie bottom of squat: net force (resultant) Concurrent forces: if one is bigger - movement, free body diagrams. Take pictures; use arrows to describe where you think forces are: static analysis. Sum of all forces on body = 0. If not 0 = unbalanced = movement o. Overcomes larger amount of friction between static and dynamic (when its moving) Horizontal; direction: green: breaking force, then we have compulsive force. Vertical: impact peak; little jolt in green, if wearing trainers; no little impact peak, blue; loading phase, big dip in blue; knee flexion little period of weightlessness, yellow; force starts to raise again blue/yellow to push off.