B.2 forces, motion and movement

kinematics

study of motion

linear motion

movement in a straight line

curvilinear motion

movement in a curve

angular rotation

movement around an axis

general movement

linear + angular movement

vector quantity

size and magnitude

scalar quantity

measures only size

angular displacement

difference between start and end positions around an axis with angular motion

force

mechanical interaction between 2 objects

what is the acceleration due to gravity on earth

9.18

newtons 1st law

interia - object will remain stationary or at a constant speed unless acted on by a force

newton’s 2nd law

F=ma

newton’s 3rd law

every action has an equal and opposite reaction

principle of stability

height of centre of mass relative to support - lower = better
position of line of gravity relative to base of support
larger mass = more stable, wider base = more support - F=ma

principle of summing joints

muscles create forces to produce movement, combining forces properly = more power

principle of linear momentum and linear impulse

The total momentum of a system remains constant if no external forces act (conservation of momentum).

principle of impulse direction

impulse is a pushing force, direction of force affects where object goes

principle of angular movement

torque, moment of inertia, angular momentum, conservation of angular momentum

torque

force applied to an object that is free to rotate around an axis

moment of inertia

how hard it is to get an object to rotate - more mass further from axis makes it harder to rotate

angular momentum

amount of potential for rotation - generated by torque

as a diver tucks into a ball, do they increase in speed or decrease

they will increase in speed as moment of inertia decreases as the mass of the diver moves closer to the centre, and angular velocity increases to maintain conservation of angular momentum

if moment inertia on an object increases, does angular velocity increase or decrease

decreases to maintain conservation of angular momentum

friction

force that acts against motion of 2 surfaces in contact, acts in opposing direction to pushing force

factors affecting how far a ball is thrown

height of release, angle of release, speed of release

what is the optimum angle of projection if the launch is lower than the landing

more than 45 degrees

what is the optimum angle of projection if the launch is higher than the landing

less than 45 degrees

what is the optimum angle of projection if the launch is the same as the landing

45 degrees

is air resistance more impactful on fast or slow moving objects

fast

why will a ball travel faster at altitude

less air particles - less air resistance

buoyancy

force acting vertically on an object immersed in water

surface drag

interaction between surface of object and fluid molecules

form drag

caused by the shape of the object - when an object moves through air/water, it creates high pressure in front and low pressure behind. the pressure difference pulls the object backward

wave drag

opposing force caused by making waves in the fluid

equation for drag

½ x coefficient drag x projected frontal area x fluid density x velocity squared

turbulent flow

when a fluid moves in an irregular way, forming swirls - causes less form drag of objects such as golf balls

bernoulli’s principle

molecules in a fluid exert less pressure the faster the travel and more pressure the slower they travel

do molecules exert more or less pressure when they travel faster

less

magnus effect

When a ball spins as it moves through air the air moves faster on one side and slower on the other side creating a pressure difference, causing the ball to curve

4 phases of movement

preparation, force production, critical instant and recovery