P1: Conservation And Dissipation

Question 1

What is energy?

Answer 1

Energy is the ability to do work

Question 2

What are all energy stores?

Answer 2

• Chemical
• Kinetic
• Gravitational Potential
• Thermal
• Elastic Potential
• Magnetic
• Electrostatic
• Nuclear

Question 3

What is chemical energy and examples?

Answer 3

The energy stored in chemical bonds between molecules
Food, cells, fuel, muscles

Question 4

What is kinetic energy and examples?

Answer 4

The energy of moving object
Runners, buses, particles colliding

Question 5

What is Gravitational Potential energy and examples?

Answer 5

The energy of an object at height
Aeroplanes, Mugs on a table, Skydivers

Question 6

What is Thermal energy and examples?

Answer 6

Thermal energy refers to the energy contained within a system that is responsible for its temperature.
Hot coffee, sun

Question 7

What is Elastic Potential energy and examples?

Answer 7

Energy stored when an object is compressed or stretched
Elastic band, spring

Question 8

What is magnetic energy and examples?

Answer 8

Energy stored when repelling charges have been moved closer
Fridge magnets, compasses

Question 9

What is electrostatic energy and examples?

Answer 9

The energy stored when opposite charges have been moved closer
Van de Graaff Generator

Question 10

What is nuclear energy and examples?

Answer 10

The energy stored in the nucleus of an atom
Nuclear reactor

Question 11

What are all energy transfers?

Answer 11

Heat
Electrical
Radiation/ waves (sound and light)
Mechanical

Question 12

What energy transfers occurs with a car brake when it stops a car

Answer 12

The car’s kinetic energy is transferred mechanically to the tires’ thermal stores, while transferring energy as sound waves.

Question 13

Explain what happens as the pendulum moves past the middle position?

Answer 13

As the pendulum reaches the middle position, the gravitational potential is at a minimum, whilst kinetic energy reaches its maximum. As the maximum height is reached, gravitational potential increases and the kinetic energy decreases

Question 14

What happens to a swinging pendulum when there is air resistance?

Answer 14

A pendulum affected by air resistance will not return to the height it was originally released at as additional energy is required to the frictional force and it will eventually stop. As the energy is transferred between gravitational potential and kinetic energy, the energy is partially transferred to thermal energy or is dissipated, gradually causing the pendulum to slow down and stop.

Question 15

What is conservation of energy?

Answer 15

Energy cannot be created or destroyed, it can only be transferred from one store to another

Question 16

What is a closed system?

Answer 16

A closed system is an isolated system in which no energy transfers take place into or out of the system

Question 17

Why does a ball not return to the height is was dropped from?

Answer 17

The bouncy ball will not return to the height it was originally dropped at due to it being affected by air resistance and as energy is transferred through mechanical transfer between gravitational potential and kinetic energy, some energy is dissipated into the surroundings through thermal and sound energy. As a result, the ball eventually slows down until it stops.

Question 18

What is work?

Answer 18

Work is the amount of energy transferred (changed) when a force moves (in the direction of the force)

Question 20

How is work calculated?

Answer 20

Work (J) = Force (N) x Distance (m)

Question 21

What is lifting force equal to?

Answer 21

The weight of the object

Question 22

What is friction?

Answer 22

Friction is an opposing force to direction of movement when two surfaces are in contact

Question 23

Why do brake pads on cars get hot?

Answer 23

Friction between the brakes pads and the wheel discs opposes rhe motion of the wheel, the force of friction does work on the brake pads and discs.
When the brakes are applied to stop the wheel the kinetic energy store transfers energy to the thermal energy store of the brake pads and discs. These become hot and transfer energy by heating to the surroundings.

Question 24

Explain the changes in energy stores a meteorite enters the Earth’s atmosphere

Answer 24

Gravitational potential: The meteorite initially has high gravitational potential energy due to its position inn the earth’s gravitational field
Kinetic energy: As the meteorite accelerates due to gravity, its gravitational potential enrrgy decreases as it is converted imto kinetic energy.

Question 25

What are the steps to investigate work done?

Answer 25

1.Lay the metre ruler on the bench. 2. Attach the Newtonmeter to the block. 3. Pull the block along the bench for one metre and record the force it took on the Newtonmeter. 4. Repeat 2 more times 5. Repeat whole investigate with rubber bands around the block.

Question 26

What is another equation for work done (often for gravitational potential)?

Answer 26

Weight(N) x Height (m)

Question 27

What is the equation for measuring change in gravitational potential energy?

Answer 27

Mass(kg) x gravitational force (N/kg or m/s^2) x height (m)

Question 28

What is kinetic energy?

Answer 28

The energy an object has because of its motion depends on its mass and velocity.

Question 29

How is kinetic energy calculated?

Answer 29

1/2 x mass x velocity^2

Question 30

How is elastic potential energy calculated?

Answer 30

1/2 x Spring constant (N/m) x extension(m) ^2

Question 31

What is Hooke's Law?

Answer 31

Hooke’s Law states that if you double the force then the extension will double

Question 32

What is useful energy?

Answer 32

Energy transferred to where it is wanted and in the form it is wanted

Question 33

What is wasted energy?

Answer 33

Wasted energy is energy that is not usefully transferred

Question 34

What happens to wasted energy?

Answer 34

Wasted energy is eventually transferred to the surroundings, which become warmer. This dissipated energy is too spread out to do useful work and so cannot be reused. This is why it is important to reduce the amount of energy that is wasted.

Question 35

What is a sankey diagram?

Answer 35

A diagram used to represent the energy input and the useful and wasted energy outputs. One large arrow (useful/wasted depending on which is larger), one smaller arrow coming off

Question 36

What does it mean to be efficient?

Answer 36

When there is a higher useful energy product than wasted energy output

Question 37

How is energy efficiency calculated?

Answer 37

Useful energy output/ Total input energy

Question 38

What is efficiency limit?

Answer 38

No device can be more than 100% efficient because you cannot create energy. You cannot get more energy out of a machine you put into it

Question 39

How may energy efficiency be increased in an engine?

Answer 39

Lubricate moving parts to reduce friction Tighten loose parts to reduce excess movement and noise

Question 40

How may energy efficiency be increased in a power cable?

Answer 40

Use short and or thicker wires to reduce electrical resistance

Question 41

How does a clockwork radio work?

Answer 41

- Turn the handle - A clockwork spring winds up - This increases the elastic potential energy of the spring as the extension is increased - The spring unwinds,energy from its elastic potential store is transferred to its kinetic store - A small electric generator them turns -Electricity is generated

Question 42

What is power?

Answer 42

Power (in physics) means the rate at which energy is transferred. It is measured in Watts, W.

Question 43

How is power calculated?

Answer 43

Energy (J)/ Time (S)

Question 44

How is power wasted calculated?

Answer 44

Total power input - Useful power output