P2 , P3 and P8

scalar quantity

only has magnitude

vector quantity

has magnitude and direction

velocity formula

displacement / time

acceleration formula with velocity and time

acceleration = change in velocity / time

acceleration formula with distance

2as = v² - u² . 2 x acceleration x distance = final velocity ² - initial velocity ²

what does gradient tell you on a distance/time graph

speed of the object

what does a flat line mean in a DT graph

object is stationary

what does a straight line going through 0 on a DT graph

the object is moving t a constant speed

what does an upwards curve mean in a DT graph

object is accelerating

what does it mean when the curve levels off in a DT graph

object is decelerating

what does a flat line on a VT ( velocity time ) graph mean

object is travelling at a constant velocity

what does the gradient of a VT ( velocity time ) graph tell you

the acceleration or deceleration of an object

what does a straight-line tell you on a VT ( velocity time ) graph

constant acceleration or deceleration

what does a upwards curve tell you in a VT ( velocity time ) graph

increasing acceleration

what does the area underneath the graph tell you in a DT graph

distance travelled

force

a push or pull that acts on an object due to the objects interactions with its surroundings

contact forces

tension, normal contact , friction

non-contact forces

electrostatic, magnetic, gravitational

resultant force

overall force acting on an object

how do you resolve 2 resultant force vectors

connect them to a right-angled triangle and its hypotenuse is the resultant force

weight formula

mass x gravitational field strength

GPE

mass x gravitational field strength x height

centripetal force

force that acts perpendicular to direction of velocity, it acts towards the centre of the circle and causes an object to move on a circular path

what would increasing the mass do to centripetal force

increase it

what would increasing the speed do to centripetal force

increase it

what would increasing the radius of orbit do to centripetal force

decrease it

newtons 1st law

a resultant force is required to change the motion of an object

a moving object that has no resultant force acting upon it will :

continue moving at the same velocity

a stationary object that has no resultant force acting upon it will :

remain stationary

newton’s second law

Force = Mass x Acceleration

newton 3rd law

when 2 objects interact, the forces they exert are equal and opposite

momentum formula

mass x velocity

conservation of momentum

total momentum before a collision = total momentum after a collision

force formula with momentum

force = change in momentum / time

force formula with mass and velocity where
m = mass
v = final velocity
u = initial velocity

force = mv-mu / time

2 safety features in a car for. crashes

airbags and crumple zones

stopping distance =

thinking distance + braking distance

conservation of energy

energy can’t be created or destroyed but rather transferred

different ways energy can be transferred

mechanical , electrical , heating, infrared, light , sound

different between open and closed system

open system can gain or lose energy

kinetic energy =

½ m x v²

transfer between KE and GPE

KE lost = GPE gained and vice versa

efficiency =

useful energy output / total energy input

how can you minimise unwanted energy transfers

lubrication and thermal insulation

difference between renewable and non renewable energy sources

renewable energy is replenished at the rate of usage

power (watts) formula

energy or work done / time

work done =

force x distance

moment

the rotational or turning effect of a force

moment =

force x perpendicular distance

biofuel

mixing recently alive organisms with ethanol

why is biofuel being considered carbon neutral controversial

it is only true if you grow plants at the rate you burn them

positive of biofuels

reliable and renewable

cons of biofuels

expensive, takes up lots of land

pros of fossil fuels

cheap and reliable

cons of fossil fuels

limited resource, produces CO2 and harmful gases

pros of nuclear energy

no pollutants, reliable, unlikely to run out for a long time

cons of nuclear energy

expensive , finite fuel , produces waste that you have to carefully store, risk of nuclear meltdown

how does solar energy work

solar cells generate electricity from sunlight

pros of wind and solar

low running costs, no pollutants

cons of wind and solar

high upfront costs, unreliable - dependent on weather

hydroelectricity

water flows down hill and is trapped by dam. let through to spin turbines connected to generators to produce electricity

tidal barrage

tide comes in and fills estuary. water is let out at controlled pace to generate electricity.

advantage of hydroelectric

renewable energy, can easily meet high demand of energy, no pollution

advantage of tidal barrage

no pollution, reliable, low running costs

disadvantages of tidal and hydroelectric

high upfront costs. they can flood land upstream

define what is meant by the unit of work

one joule of work is done on an object when a force of one newton causes its displacement to change by one metre

elastic collisions

objects moves in opposite directions and the velocities are different

inelastic collisions

object moves in same direction and the velocities are identical

how do airbags reduce injury

it increases impact time and reduces force

when is mechanical work done

when a force acts on an object

when is electrical work done

A charge moving through a potential difference (e.g. current)

heating - by particles transfer

Energy is transferred from a hotter object to a colder one

(Heating by) radiation

Energy transferred by electromagnetic waves (e.g. visible light)

kinetic energy store

Moving objects have energy in their kinetic store

Gravitational

Objects gain energy in their gravitational potential store when they are lifted through a gravitational fiel

Elastic

Objects have energy in their elastic potential store if they are stretched, squashed or bent

Magnetic

Magnetic materials interacting with each other have energy in their magnetic store

Electrostatic

Objects with charge (like electrons and protons) interacting with one another have energy in their electrostatic store

Chemical

Chemical reactions transfer energy into or away from a substance's chemical store

Nuclear

Atomic nuclei release energy from their nuclear store during nuclear reactions

Thermal

All objects have energy in their thermal store, the hotter the object, the more energy it has in this store

inertia

tendency of an object to continue in a state of rest or in a uniform motion unless acted on by an external force

inertial mass

how difficult it is to change the velocity of an object

centripetal force

resultant perpendicular force towards the centre of the circle to keep a body in uniform circular motion

weight

force acting an object due to gravitational attraction

mass

how heavy the total matter of an object is

stopping distance

The total distance travelled during the time it takes for a car to stop in response to some emergency

Thinking distance

the distance travelled in the time it takes the driver to react(reaction time) in metres

Braking distance

the distance travelled under the braking force in metres

measuring reaction time

hold a ruler at 0cm and then have someone drop it unexpectedly, the larger the distance the greater reaction time

factors affecting braking distance

speed of car - faster = greater braking distance

vehicle condition - worn tyres / poor brakes = greater braking distance

vehicle mass - heavier = greater braking distance

road condition - wet or icy roads = greater braking distance

factors affecting thinking distance

tiredness

distractions

intoxications - alcohol or drugs

car speed

breaking distance is proportional to

velocity²

GPE

energy an object has due to its height in a gravitational field

KE

amount of energy an object has as a result of its mass and speed

useful energy

energy transfer that serves intended purpose

wasted energy

an energy transfer that is not useful for intended purpose and is dissipated to surroundings

dissipation

when energy spreads out wastefully

how does lubricaton reduce wasted energy transfers

it reduces the amount of friction by lubricating moving parts and reduces the amount of energy that is transferred to the thermal energy store

how does thermal insulation reduce wasted energy transfers

it stops energy transfer of heat through conduction and therefore reduces the cooling rate meaning more heat is retained and less wasted energy transfers