physics

Question 1

what happens when energy is transferred to an object?

Answer 1

The energy is stored in one of the object energy stores

Question 2

what are the 8 energy stores?

Answer 2

-Thermal
-Kinetic
-Gravitational
-Elastic potential
-Nuclear
-Magnetic
-Chemical
-Electrostatic

Question 3

What are 2 ways energy is transferred?

Answer 3

-Mechanically (by a force doing work)
-Electrically (by heating or radiation eg light/sound)

Question 4

what is a system?
what happens when a system changes?
what are closed systems and the net change?

Answer 4

-An object or a group of objects
-When a system changes energy is transferred it can be transferred into or away from the system or between different objects in the system or between different types of energy stores
-Closed system are systems where neither matter nor energy can enter or leave.Net change in the total energy is 0

Question 5

What is work done and how can it be done?

Answer 5

-Work done is when energy has been transferred from one store to another
-It can be done when currents flow or by a force moving an object

Question 6

what is kinetic energy?
how do you know when energy is transferred to kinetic energy?
what does the energy in kinetic energy store depend on?
what does greater mass mean in kinetic?

Answer 6

-Anything that is moving has energy in it
-When an object speeds up and is transferred away from this store when an object slows down
-Depends on mass and speed
-The greater the mass the faster its going, more energy

Question 7

what is the formula of kinetic energy?

Answer 7

Ek=0.5 x mass x speed squared (j)
Mass=kg
speed=m/s

Question 8

what is gravitational energy?
what does the amount of energy store depend on?
what is the formula of gravitational potential energy?

Answer 8

-lifting an object requires work, the higher the object is lifted the more energy is transferred
-Depends on mass, height and strength
FORMULA:
Ep=mgh
Mass=kg
Height=metres
Gravitational field strength=N/kg

Question 9

what happens when an object falls?
when there is no air resistance in a falling object what does it mean?
what happens to the air resistance in real life?

Answer 9

-when something falls energy from its gravitational potential is transferred to kinetic energy store
-Energy lost from gpe=energy gained in kinetic energy
-Air resistance acts against falling objects it causes some energy to be transferred to other energy stores

Question 10

what is elastic potential energy?
what is the formula?

Answer 10

-Stretching or squashing an object can transfer energy to elastic potential
-Ee=0.5 x spring constant x extension squared
K=spring constant n/m
extension squared=metres

Question 11

what is the rule of conservation energy?
what happens when energy is transferred?

Answer 11

-Energy can be transferred usefully stored or dissipated but can never be created or destroyed
-when energy is transferred between stores not all the energy is transferred usefully into the store that you want it to go

Question 12

what is dissipated energy?

Answer 12

-Dissipated energy sometimes called wasted energy because the energy is being stored a way that is not useful

Question 13

what is power?
what is it measured in?
what is equation

Answer 13

-Rate of energy transfer or rate of doing work
-Power is measured in watts. One watt = 1 joule of energy transferred per second
EQUATIONS
p=e/t
E=energy transferred (j)
t=time (s)
OR
p=w/t
Work done=(j)

Question 14

what are two examples of energy being wated and energy in a closed system?

Answer 14

-Mobile phone is a system when you use the phone energy is usefully transferred from the chemical energy store of the battery in the phone .But some of the energy is dissipated in this transfer to the thermal energy store of the phone (hot)
-Closed system: A cold spoon is dropped into an insulated flask of hot soup you can assume that the flask is a perfect thermal insulator so the spoon and soup form a closed system .Energy is transferred from the thermal energy store of the soup to the useless thermal energy store of the spoon
no energy has left the system-net change is 0

Question 15

what happens whenever something moves and what does it cause?

what does lubricants do when object are being rubbed together?

what is lubricants?

Answer 15

-Theres usually 1 frictional force acting against it.This causes some energy to be dissipated
-Lubricants can be used to reduce the friction between the objects surfaces when they move
-Lubricants are liquids so they can flow easily between objects and coat them

Question 16

what happens when an object is being heated and what does it cause?
what is conduction?

Answer 16

-When an object is being heated energy is transferred to kinetic energy store of its particles.
This causes the particles to vibrate more and collide with each other.During these collisions energy is transferred between particles kinetic energy stores

Question 17

what is thermal conductivity?
what do materials with high thermal conductivity do?

Answer 17

-Thermal conductivity is a measure of how quickly energy is transferred through a material in this way
-Materials with high thermal conductivity transfer energy between their particles at a faster rate

Question 18

what is convection?

Answer 18

-Because liquids and gases can flow the warmer and less dense region will rise above denser cooler regions.So energetic particles move away from hotter to cooler regions

Question 19

what are 2 things to prevent energy losses through heating?

Answer 19

-Having thick walls. The thicker the walls the lower the thermal conductivity the slower the rate of energy will be.(cool more slowly)
-Use thermal insulation

Question 20

what are 4 examples of using thermal insulation?

Answer 20

-Cavity walls made up of inner and outer wall with an air gap in the middle. The air gap reduces the amount of energy transferred by conduction through the walls. Cavity wall insulation where the cavity wall air gap is filled with a foam can also reduce energy transfer by convection in the wall cavity

-Loft insulation can reduce convection currents (a cycle where air particles are constantly being heated, rising cooling, sinking being created in lofts

-Double glazed windows work the same way as cavity walls they have an air gap between two sheets of glass to prevent energy transfer by conduction through the windows

-Draught excluders around doors and windows reduce energy transfers by convection

Question 21

why are useful device only useful?
why are input energy usually wasted?
what are three ways to improve effiency?

Answer 21

-Because they transfer energy from one store to another
-This is because they are transferred to a useless energy store (thermal)
-3 ways to improve:
-Insulating objects
-More streamlined
-Lubricating them

Question 22

what are 2 equations for effiency?

Answer 22

• Effiency=useful output energy transfer
  DIVIDED
  Total input energy transfer

-Effiency= useful power output
DIVIDED
total power output

Question 23

why is electric heaters 100 percent efficient?
what happens ultimately to energy at the end?

Answer 23

-This is because all the energy in the electrostatic energy store is transferred to useful thermal energy stores
-Ends up being transferred to thermal energy stores