p1 conservation and dissipation of energy

Question 1

name the eight energy stores

Answer 1

kinetic, gravitational potential, elastic potential, thermal, chemical, nuclear, magnetic, electrostatic

Question 2

kinetic

Answer 2

energy an object has because it is moving

Question 3

gravitational potential

Answer 3

energy an object has because of its height above the ground

Question 4

elastic potential

Answer 4

energy an elastic object has when it is stretched or compressed

Question 5

thermal (or internal)

Answer 5

energy an object has because of its temperature (the total kinetic and potential energy of the particles in the object)

Question 6

chemical

Answer 6

energy that can be transferred by chemical reactions involving foods. fuels, and the chemicals in batteries

Question 7

nuclear

Answer 7

energy stored in the nucleus of an atom

Question 8

magnetic

Answer 8

energy a magnetic object has when it is near a magnet or in a magnetic field

Question 9

electrostatic

Answer 9

energy a charged object has when it is near another charged object

Question 10

name the four ways in which energy can be transferred

Answer 10

heating, waves, electric current, mechanically ( by forces)

Question 11

what is a system?

Answer 11

an object or group of objects

Question 12

what is a closed system?

Answer 12

a system where no energy can be transferred to or from the surroundings - the total energy in the system stays the same

Question 13

what is work done?

Answer 13

energy transferred when a force moves an object

Question 14

what is the unit for energy?

Answer 14

joule ( J )

Question 15

equation for kinetic energy

Answer 15

kinetic energy (j) = 0.5 x mass (kg) x (speed)2

Question 16

gravitational potential energy equation

Answer 16

gravitational potential energy (j) = mass (kg) x gravitational field strength (N/kg) x height (m)

Question 17

power equation

Answer 17

power (w) = energy transferred (j) / time (s)
or
power (w) = work done (j) / time (s)

Question 18

what is one joule of work?

Answer 18

the work done when a force of 1N causes an object to move 1m in the direction of the force

Question 19

describe the energy transfer when a moving car slows down

Answer 19

energy is transferred mechanically from the kinetic store of the car to the thermal store of its brakes - some energy is dissipated to the thermal store of the surroundings

Question 20

describe the energy transfer when an electric kettle is used to heat water

Answer 20

the electric current in a kettle transfers energy to the heating element’s thermal store - energy is then transferred by heating from the heating element’s thermal store to the thermal store of the water

Question 21

describe the energy transfer when a ball is fired using an elastic band

Answer 21

energy is transferred mechanically from the elastic store of the elastic band to the kinetic store of the band - some energy is dissipated to the thermal store of the surroundings

Question 22

describe the energy transfer when a falling apple hits the ground

Answer 22

energy is transferred from the kinetic store of the apple and dissipated to the thermal store of the surroundings by sound waves

Question 23

name the unit that represents one joule transferred per second

Answer 23

watt (w)

Question 24

what does a material’s thermal conductivity tell you?

Answer 24

how well it conducts heat

Question 25

which materials have low thermal conductivity?

Answer 25

thermal insulators

Question 26

give three factors that determine the rate of thermal energy transfer through a material

Answer 26

thermal conductivity of material, temperature difference, thickness of material

Question 27

what factors affect the rate of heat loss from a building?

Answer 27

thickness of walls and roof, thermal conductivity of walls and roof, the temperature difference between two sides of wall/roof

Question 28

what is efficiency

Answer 28

efficiency is a measure of how much energy is transferred usefully

Question 29

efficiency equation

Answer 29

efficiency = useful output energy transfer (j) / total input energy transfer (j)
or
efficiency = useful power output (w) / total power input (w)

Question 30

energy transfers - heating

Answer 30

energy is transferred from one object to another object with a lower temperature

Question 31

energy transfers - waves

Answer 31

eaves (e.g., light and sound waves) can transfer energy by radiation

Question 32

energy transfers - electricity

Answer 32

when an electric current flows it can transfer energy

Question 33

energy transfers - forces (mechanical work)

Answer 33

energy is transferred when a force moves or changes the shape of an object