physics topic test

speed

is the measure of how fast something moves

average speed

is a measure of how fast something moves overall

instantaneous speed

your speed at a particular instant

m/s → km/hr

times by 3.6

speed formula

average speed (v)= distance travelled (m)/ time taken (s)

distance

the total length covered in a journey (scalar quantity)

displacement

the straight line length from the START to the FINISH of a journey with the direction stated (vector quantity)

scalar quantity

a measurement with magnitude only

vector quantity

a measurement that has magnitude and direction

what are si units?

systeme international- intl system of units that are used universally so that scientists from anywhere can agree in measurements used

how do i place vectors?

from head to tail

newtons first law

An object at rest remains at rest, or if in motion remains in motion at a constant velocity unless acted on by a net external force

intertia

the tendency to resist any change in motion is called intertia

inertia examples

when a train moves and you seem to fall backwards

force

a push, pull or a twist

newtons second law

The acceleration of an object is directly related to the net force and inversely related to its mass

mass

mass is a measure of the amount of matter in an object

SI unit for force

newtons

effects of a force

change in motion or a change in shape

contact forces

physical- a push or a pull

non-contact forces

gravity/magnetism

what happens when the net force is 0?

the object doesn’t accelerate (stay at rest or move at a constant velocity)

what happens when the net force isn’t 0?

the object will accelerate (speed up or slow down).

what is gravity?

the attractive force that acts between masses (attracted to each other with equal force)

what is weight?

weight is the force of a mass placed in a gravitational field

newtons 3rd law

for every action force there is an equal and opposite reaction force

what is important to note about newtons third law?

the 2 forces act on different objects, they do not cancel each other out

reaction and force pairs: boy trips and hits wall

action: boy hits wall
reaction: wall hits boy

reaction and force pairs: girl pushes boy

action: girl pushes boy
reaction: boy pushes girl

reaction and force pairs: car wheels turning on tarmac

action: wheels push backwards into the road
reaction: road pushes car forward

why is there no propulsion when car wheels are turning on ice?

There is no action or reaction force because no friction is availabale to transfer the forces

reaction and force pairs: releasing an untied balloon

action: air particles hit the balloon pushing it forwards
reaction: the balloon hit the air particles pushing it backwards

reaction and force pairs: your weight pulls you down when you free fall out a plane

Earth pulls you down with the force of gravity

You pull the earth upward with an equal and opposite gravitational force

principle of conservation of energy

energy can’t be destroyed, only transferred or transformed