3.2 - energy

Question 1

when is work done

Answer 1

when energy is transfered from 1 store to another

Question 2

whats the equation linking work force and distance

Answer 2

work done= forcex distance

Question 3

whats the unit for work

Answer 3

joules

Question 4

energy is transfered when..

Answer 4

work is done

Question 5

what is power

Answer 5

the rate at which energy is transfered or rate at which work is done

Question 6

whatre the 2 equations for power

Answer 6

p=energy/time
or
p=work/time

Question 7

whats the unit for power

Answer 7

watts

Question 8

whats the formula for gravitational potential energy `(J)

Answer 8

massXgravityXheight

Question 9

what is gravitational potential energy

Answer 9

the energy stored in a object due to its positition above earths surface due to gravity acting on an object

Question 10

what happens when a system changes

Answer 10

energy is transfered

Question 11

energy cannot be created nor…

Answer 11

destroyed

Question 12

what is kinetic energy

Answer 12

the energy stored in moving objects

Question 13

whats the formula for kinetic energy

Answer 13

1/2 x mass x v^2

Question 14

what is elastic potential energy

Answer 14

energy stored in elastic objects when work is done on the object

Question 15

how do u calculate the elastic potential energy in a stretched spring

Answer 15

1/2 x spring constant x extension ^2

Question 16

what happens if a spring reaches its elastic potential

Answer 16

it wont be reverted to its normal shape

Question 17

whatre the 3 things that can happen to energy

Answer 17

transferred usefully, stored or dissipated, but cannot be created or destroyed.

Question 17

what happens when energy is transfered

Answer 17

only part of it may be usefully transferred; the rest is dissipated so that it is stored in less useful ways. This energy is often described as being ‘wasted’.

Question 18

what 2 forces dissipate energy by heating their surroundings

Answer 18

friction and air resistance

Question 19

whatre the 2 ways efficiency of a device can be calculated

Answer 19

efficiency = useful energy out /total energy in x100
and
efficiency = useful power out / total power in x 100

Question 20

how can energy flow in systems be represented

Answer 20

Sankey diagrams.

Question 21

whatre the factors that effect fossil fuel selection

Answer 21

ease of storage, energy content and safety.

Question 22

what happens when fuels are used

Answer 22

some energy is transferred to the surroundings. Some fuels are more efficient than others.

Question 23

whatre the impacts of using fuels

Answer 23

renewability and the environmental impacts of extraction, use and disposal.

Question 24

whatre some of 3 renewable energy stores

Answer 24

wave power, solar power and geothermal power.