p1 : energy

Question 1

What is a system?

Answer 1

A system is an object or group of objects.

Question 2

What happens to the energy in a system when the system changes?

Answer 2

The way the energy is stored changes.

Question 3

What are the energy store changes when a ball is thrown upwards?

Answer 3

the person throwing the ball supplies kinetic energy which causes the ball to rise. the ball slows down as it rises, which causes the store of kinetic energy to transfer to gravitational potential energy.

Question 4

What are the energy store changes when a moving object hits an obstacle?

Answer 4

the moving object has a store of kinetic energy which is transferred to other stores when it hits the obstacle and suddenly stops. some of these stores include elastic potential energy in squashing objects and vibrational energy as a sound is emitted.

Question 5

What are the energy store changes when an object is accelerated by a constant force?

Answer 5

when a constant force is applied across a distance, work is done on the object. this work is transferred to a store of kinetic energy in the object causing the object to move.

Question 6

What are the energy store changes when a vehicle applies its brakes to slow down?

Answer 6

a moving vehicle has a store of kinetic energy and when the brakes are applied there is a large amount of friction. as this happens heat energy is released.

Question 7

What are the energy store changes when water is boiled in an electric kettle?

Answer 7

the kettle transfers a store of electrical energy to heat energy, which is transferred to the water to heat it up as the molecules have more vibrational energy.

Question 8

If 500 J of electrical energy is used by a kettle, how much heat energy will the water have gained?

Answer 8

500 J

Question 9

What store of energy is associated with movement?

Answer 9

Kinetic energy

Question 10

What is the word equation for kinetic energy?

Answer 10

kinetic energy = ½ x mass x (speed)²

Question 11

What are the units of kinetic energy?

Answer 11

Joules, J

Question 12

What store of energy is associated with a stretched spring?

Answer 12

Elastic potential energy

Question 13

Give the word equation for elastic potential energy?

Answer 13

elastic potential energy = ½ x spring constant x (extension)²

Question 14

What are the units of elastic potential energy?

Answer 14

Joules, J

Question 15

What store of energy is associated with the height of an object above ground level?

Answer 15

Gravitational potential energy

Question 16

Give the word equation for gravitational potential energy?

Answer 16

g p e = mass x gravitational field strength x height

Question 17

What are the units of gravitational potential energy?

Answer 17

Joules, J

Question 18

What is the store of energy that is associated with temperature changes?

Answer 18

Thermal energy

Question 19

Give the word equation for the change in thermal energy?

Answer 19

change in thermal energy = mass x specific heat capacity x temperature change

Question 20

What is the unit of specific heat capacity?

Answer 20

J/kg °C

Question 21

What is the specific heat capacity of a substance?

Answer 21

It is the amount of energy required to raise the temperature of 1 kg of the substance by 1 °C.

Question 22

In the specific heat capacity required practical, why is it important to insulate the block?

Answer 22

So that all of the thermal energy transferred to the block is used to increase its temperature, and is not dissipated to the surroundings.

Question 23

What is the definition of power?

Answer 23

Power is defined as the rate at which energy is transferred or the rate at which work is done.

Question 24

What is the unit of power?

Answer 24

Watts, W

Question 25

What does 1 Watt mean?

Answer 25

An energy transfer of 1 Joule per second.

Question 26

Compare the power of two electric motors that both lift the same weight through the same height but one does it faster.

Answer 26

The one which does it faster has the greater power.

Question 27

What is the principle of conservation of energy?

Answer 27

Energy cannot be created or destroyed, it can only be transferred usefully, stored or dissipated.

Question 28

When there are energy transfers in a closed system, what happens to the total energy of the system?

Answer 28

There is no net change to the total energy.

Question 29

What does it mean when we say that energy is 'wasted'?

Answer 29

in all system changes energy is dissipated so that it is stored in less useful ways - such as thermal energy.

Question 30

Give some examples of how to reduce unwanted energy transfers.

Answer 30

* Thermal insulation * Lubrication

Question 31

What does thermal conductivity mean?

Answer 31

The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material.

Question 32

What factors affect the rate of cooling of a building?

Answer 32

Thickness and thermal conductivity of its walls.

Question 33

In the insulation required practical, what is the independent variable?

Answer 33

The type and thickness of insulating materials

Question 34

What does the efficiency of an energy transfer tell?

Answer 34

How much of the input energy is transferred usefully.

Question 35

What is the definition of a renewable energy resource?

Answer 35

It is one that can be replenished as it is used.

Question 36

What are some examples of renewable energy resources?

Answer 36

* Biofuel * Wind * Hydro-electricity * Geothermal * Tidal * Solar * Wave

Question 37

What is the definition of non-renewable energy?

Answer 37

It is one that cannot be replenished.

Question 38

What are some examples of non-renewable energy resources?

Answer 38

* Fossil fuels (coal, oil, natural gas) * Nuclear

Question 39

What are some uses of energy resources?

Answer 39

* Transport * Electricity generation * Heating

Question 40

Why are some energy resources more reliable than others?

Answer 40

Some resources rely on the weather (such as solar and wind power) which may not always be favourable, but some resources are always accessible

Question 41

What environmental impact do some resources cause?

Answer 41

Burning fossil fuels and biofuel release CO2 into the atmosphere which contributes to global warming.

Question 42

Although we know that these environmental issues arise, why can we not always deal with them?

Answer 42

There may be political, social, ethical or economic considerations.

Question 43

what is the symbol equation for kinetic energy.

Answer 43

Ek = 1/2mv²

Question 44

what is the symbol equation for elastic potential energy

Answer 44

Ee = 1/2ke²

Question 45

what is the symbol equation for gravitational potential energy (GPE)

Answer 45

Ep = Mgh

Question 46

what is the symbol equation for the change in thermal energy

Answer 46

ΔE = mcΔT

Question 47

what is the word equation for power

Answer 47

power = energy transferred / time

Question 48

what is the symbol equation for power

Answer 48

p = E / T

Question 49

what is the word equation for efficiency of an energy transfer

Answer 49

efficiency = useful output energy transfer / total input energy transfer

Question 50

what is the word equation for efficiency of a power output

Answer 50

efficiency = useful power output / total power input

Question 51

how can the efficiency of an energy transfer be increased

Answer 51

by using lubrication or insulation