Linear Momentum  M = mv  measure of the quantity and direction of the motion of a body  measure of a body’s persistence in its state of motion

Linear Impulse = Ft Force x time of force application greater F or longer t = greater change in M Impulse-Momentum equation Ft = M2 - M1

Shock Absorption  landing from a jump or catching a ball require limb flexion to “cushion” impact  Gradual stop --> M = force x TIME  Sudden stop --> M = FORCE x time  GRF in downhill running more than uphill  GRF in high and low impact Aerobics

Change Direction: Ft new Ft in a different direction required quickest change = large F for small t less massive person = change easier

Ft and Acceleration Acceleration can only occur if F-motive is greater than F-resistive longer t of motive F application = M M M preparation phase in jump, throw, strike = increase t of force application during the execution phase

Ft Momentum in Human Motion  For shock absorption, spread the force over a long period of time  e.g. catching, landing pits  For quick starts, fast running/skating, etc. apply a LARGE force for a short period  study on world class & university sprinters

Collisions- implement/projectile resultant v of projectile depends on: 1. Ft applied by implement 2. Elastic recoil capabilities of projectile impact time on projectile is brief (.001 to.005 sec.) therefore F must be LARGE

Tennis Racquet & Ball Collision each receives equal/opposite Ft from other v change for ball is large - smaller m ball stops, deforms, accelerates away v change in racquet is small - larger m racquet slows but does not impact total M of ball/racquet same after impact since M lost by racquet is gained by ball

Human Body Collision Conservation of M means each body in a collision will experience a change in M change in M will be in the form of a change in the v of each body less massive person will experience a greater change in v - “sudden stop”

page 396 “Basic Biomechanics” 4 th edition by Susan J. Hall Head-on Collision Two Players Player 1: m = 90kgv = 6 m/s Player 2: m = 80kgv = 7 m/s Resultant v after collision: 0.12 m/s in the direction of 80kg player

Kinetic Energy: KE = ½ mv²  Energy = ability to do work  Kinetic Energy = ability of a body to apply force to move or deform another body  squared v makes this component important  higher up = greater a downward  faster forward = greater impact