Biomechanics - Force, impulse and linear momentum

Rolling friction

Allows wheels to roll but not slip eg bike

Newton's First Law (law of inertia)

An object either remains at rest or continues to move at a constant velocity, unless acted upon by a net force.

Newton's second law

F = ma. The rate of change of a body is proportional to the force causing it and the change takes place in the direction in which the force acts.

Friction

F=uN

Newton's third law

For every action force, there is a reaction force which is equal in magnitude but opposite in direction.

Impulse

Force x time. Also change in momentum (mv - mu), represented by the area under a force-time graph. Use trapezium rule (A = 1/2 x (h1 + h2) x d) to calculate. ALSO impulse / mass = change in velocity

Pythagoras

How to calculate resultant forces

Limiting friction

Stops something moving eg parked car

Sliding friction

Slows you down to a stop eg ice skater

Force (N)

The pushing or pulling action that one object exerts on another. A 1N force produces 1ms-2 acceleration in a 1kg mass.

External forces

eg gravity, contact with ground. Easier to measure eg force plates.

Internal forces

eg muscle forces, joint forces. Difficult to measure as invasive.

Weight

Mass x gravitational pull. A body is weightless in freefall as there are no external forces acting on it.

Linear momentum (kgms-1)

Mass x velocity

Linear kinetics

The study of the effects of forces on the motion of bodies.