Energy

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Kinetic energy :

E(k) = 0.5 * mass* v2

(J) (KG) (m/s)

chemical reaction in engine some converted to kinetic energy store as the car moves

when you apply a force to a spring we are doing work to change the shape ie the length of the spring

when applying a force it is called doing work

elastic potential energy is being stored in the spring as it is stretched

stretch is the extension (e)

extension against force straight line through zero they are directly proportional

the spring has been stretched beyong the limit of proportionality it will no longer return to its original shape

DONT LEARN THE FORMULA

the extension has to be in m

E(e)= 0.5 *K*e2

(J) ( N/m)

gravitational potential energy is due to the force of gravity acting on the object

NOT GIVEN THIS EQUATION SO LEARN IT :

E(p)= mgh

g= (N/KG) height is in m and mass in KG and obviously energy in Joules

given specific heat capacity in exam :

elastic potential energy is the energy stored in a stretched spring

thermal energy is the energy stored due to an objects temperature

energy can be transferred usefully, stored or dissipated but cannot be created or destroyed

air particles is also a system

closed system is where no energy can enter or leave

friction causes energy to be transferred to thermal energy- dissipated and can go to air

swing with less energy do to thermal

reduce friction to reduce unwanted energy transfers

use oil as a lubricant or remove air particles

start GPE as he falls energy to KE store when rope starts to tighten KE is at its maximum

rope fully extended KE is 0 elastic potential energy store rope recoils back to KE store then KE TO GPE store at top of ascend all of energy is in the GPE store

jumper never returns back to original position energy lost in thermal energy store due to friction with air particles

stretching affects in rope not fully elastic - thermal energy during stretching and recoil

mechanical work involves a force to move an object

electrical work involves a current transferring energy

work done = force * distance LEARN THIS

brake presses on wheels of the car friction between these the KE is transferred to THERMAL energy to brakes temp of brakes increases and the car slows down and stops

power = energy transferred / time

power = work done / time

time in seconds

work done and energy is in joules

power is in watts

LEARN THESE ^^ not given in exam

1 Watt is an energy transfer of 1 joule per second

efficiency = useful energy output / total energy inut

efficiency = useful power output/ total power input

NOT GIVEN LEARN THESE

reduce thermal energy loss when cooking to use a pan with a wider base and a lid unwanted transfer of thermal energy

a lot of thermal energy is used to heat the base of the pan itself so instead place the heating element inside the water

plastic is a more efficient way of heating water than a pan

put a insulating material in the cavity with a low thermal conductivity to reduce heat loss

double glazed windows low thermal conductivity

less thermal energy can pass through

loft insulation for roof

build houses with thick walls reduces the rate of thermal energy

Required practical specific heat capicity

zero the balance and measure mass of oil using a balance

place a thermometer and immersion heater into the oil

read the starting temperature of the oil

wrap the beaker with insulating foam reduces the energy transfer to surroundings

connect joulemeter and power pack to immersion heater

leave for 30 mins

read no of joules into immersion heater and final temp of the oil

calculate specific heat capacity

inaccuracy

thermal energy out of beaker into air use lower thermal conductivity material

not all of immersion heater to oil FULLY SUBMERGED

not reading thermometer properly electronic temp probe

thermal energy may not be spread through the oil SO STIR THE OIL

required practical thermal insulator

Place small beaker into large beaker

transfer hot water to small beaker

use piece of cardboard as a lid for the large beaker with a hole for the thermometer

record start temp and start stopwatch record temp every 3 mins for 15 mins

same volume of hot water use insulating materials different ones USE SAME MASS and area

place it in gap between large and small beaker independant variable is the type of material

dependant is the temp

control is the volume of water and mass of material and keep start temp of water the same- kettle

plot cooling curves

investigate thickness

repeat and wrap 2 layers of material and repeat with 4 and 6 layers independant is number of layers of newspaper

more effective thermal insulator rate of decrease is slower

fossil fuels are reliable provide energy when we need it

release great deal of energy for aeroplanes

abundant still has plenty of them and relatively cheap