Conservation and dissipation of Energy - Topic 1

Question 1

Name the 8 energy stores

Answer 1

kinetic, thermal, GPE, EPE, chemical, nuclear, magnetic, electrostatic
Eating Noodles Energises The Grannies Killing More Children

Question 2

What is a system?

Answer 2

A single object or a group of objects

Question 3

What is a closed system

Answer 3

They are systems where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero.

Question 4

Magnetic energy is…

Answer 4

energy stored between the poles of magnetic objects

Question 5

What are the 4 types of energy transfer?

Answer 5

-by radiation: waves carrying energy (e.g. light)
-** by heating**: conduction/ convection
- mechanically: (by forces), push or pull (physical movement )
- electrically: anything which uses electricity

Question 6

Work done=?

Answer 6

force x distance

Question 7

What is work done?

Answer 7

when energy is transferred from one store to another

Question 8

Work done is measured in what?

Answer 8

Joules

Question 9

Useful energy can be radiated as what?

Answer 9

Light

Question 10

Sound is a form of which energy store?

Answer 10

kinetic

Question 11

Kinetic energy =?

Answer 11

1/2 x mass x velocity squared (= 1/2 m v^2)

Question 12

What is kinetic energy measured in?

Answer 12

Joules

Question 13

GPE =?

Answer 13

mass(kg) x gravitational field strength(N/kg) x change in height(m)
= m g h

Question 14

A value of what is most commonly used for the Earth’s gravitational field strength?

Answer 14

10

Question 15

Change in height is always measured in what?

Answer 15

Metres

Question 16

Energy lost from the g.p.e. store = ?

Answer 16

Energy gained in the kinetic energy store

Question 17

Elastic potential energy(J) = ?

Answer 17

1/2 x spring constant (N/m)x extension squared(m)
= 1/2 k e^2

Question 18

Energy is most commonly lost in what store due to what?

Answer 18

Thermal, friction

Question 19

What is the spring constant ?

Answer 19

A value which tells us how easily stretched a spring is
- different metals/thickness effects the spring constant

Question 20

In order to waste less energy, do what?

Answer 20

• slow down
• lubricate moving parts: to reduce friction and flow more easily between objects and coat them e.g. oils,

Question 21

What is dissipation?

Answer 21

When energy is lost to its surroundings

Question 22

Sound waves carry energy away. True or false?

Answer 22

True

Question 23

Efficiency is what?

Answer 23

how much of the original energy is used usefully

Question 24

Efficiency =?

Answer 24

= useful energy output/total energy input
OR
= useful power output / total power output

Question 25

What does an efficiency of 1 mean?

Answer 25

no energy is wasted in the system

Question 26

What is power?

Answer 26

The rate of energy transfer, or the rate of doing work

Question 27

Power (Watts) = ?

Answer 27

= Energy transferred (J) / time (s)
OR
= Work done (J) / time (s)

Question 28

How can you improve the efficiency of energy transfers?

Answer 28

• insulating objects
• lubricating moving objects
• more streamlined

Question 29

How can you insulate your house from heat dissipation?

Answer 29

• thick, low thermal conductivity walls : the thicker and lower the conductivity is the slower the rate of energy transfer

Question 30

what is the principle of conservation of energy

Answer 30

energy can be stored, transferred between stores and dissipated, CANNOT be created or destroyed

Question 31

what is the energy transfer stores of a ball rolling up a slope

Answer 31

energy transferred mechanically :
- **kinetic —> gravitational potential*
- some energy is transferred mechanically to the thermal energy stores of the ball and the slope due to friction

Question 32

describe the energy store transfers of a moving object hitting an obstacle

Answer 32

• obstacle kinetic energy –> moving objects kinetic energy
  -some kinetic energy of obstacle is transferred to thermal energy store of object and obstacle
• rest energy is wasted to sound

Question 33

describe the energy store transfers of an electric kettle boiling water

Answer 33

Energy transfers electrically from the electrical store of the mains power supply to the thermal store of the water.
- some energy wasted to thermal energy store of the surroundings

Question 34

describe the energy transfer of an object accelerated by a constant force

Answer 34

• Work is done by a force on an object.
• work done –> kinetic store.

Question 35

describe the energy transfer of a vehicle slowing down

Answer 35

• when moving energy is inkinetic store
  when decelerates, energy transferred from kinetic –> thermal sore of the surroundings (dissipated)
• energy transferred by heating due to friction

Question 36

energy transfer by heating can happen in 3 different ways:

Answer 36

• radiation
• conduction
• convection