biomechanics

biomechanics topic

force (F)

force (F)

- push or pull on an object

- F=ma (mass x acceleration

- newton (N)

speed (s)

- rate at which an object covers distance

- s=d/t (distance/time)

- only scalar

- km/h

velocity (v)

- rate at which an object changes position (direction aware)

- v=d/t (displacement change/time)

- m/s

displacement (S)

- shortest distance between initial and final point

- m

acceleration (a)

- rate of change of velocity (speed/direction) per second

- m/s/s

momentum (P)

- amount of motion possessed by a moving object

- MxV (mass x velocity)

- kg m/s

impulse (J)

- duration that force is applied from momentum of an object

- force x time

centre of mass

point in which the mass of a body is evenly distributed

centre of gravity

point at which gravity is acting

first class lever

- fulcrum in middle

- magnify force applied and/or generate speed

- head joining top of vertebral

- seesaw

second class lever

- load in middle

- increase strength that humans apply to objects

- foot/lower leg in jumping actions

third class lever

- effort in middle/force applied in middle

- speed advantage

- almost all levers in human body are 3rd class

parts of lever in the body

fulcrum: joint

effort: muscles

load: resistance, gravity, weight

newton’s first law

an object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force

first law examples

- soccer ball wont move from position it's placed until a player applies force by kicking it

- a tennis ball will continue travelling in the direction of the serve until the player at the other end applies a force and hits it back

newton’s second law

acceleration is proportional to and in the same direction as the unbalanced force applied to it

second law examples

- two identical shot puts are acted on by an unbalanced force (thrown), one by olympic athlete, one by beginner, one thrown with greater force will have greater acceleration.

newton’s third law

every action has an equal and opposite reaction

third law examples

- gymnast pushes down on bars, bars push back on gymnast with equal force

- basketball hits the backboard at an angle, will bounce on an angle with similar force to that with which it was thrown

- basketball dribble

- swimmer freestyle, hand travels downwards in water, propels them upward with equal and opposite reaction

law of conservation of mass

- when two objects collide, the total momentum of the objects before the collision is equal to the total momentum of the objects after the collision

angular momentum

• quantity of rotation about an axis

• moment of inertia x angular velocity

moment of inertia

• mass

• distribution of mass about the axis

• further mass is spread, increased moment of inertia

angular velocity

• speed of rotation about an axis

• degrees/second

torque

a twisting force that causes rotation

bernoulli’s principle

there is an inverse relationship between velocity and pressure

magnus effect

the deviation from linear flight path due to spin