TOPIC 1 Energy

Question 1

Define energy

Answer 1

If an object has energy, it has the ability to make other objects move.

Question 2

Name the 8 energy stores

Answer 2

Thermal energy stores
Kinetic
Gravitational Potential
Elastic potential
Chemical
Magnetic
Electrostatic
Nuclear

Question 3

What does the total energy of a system equal

Answer 3

Total amount of energy in = total amount of energy out

Question 4

What happens to energy during an energy transfer

Answer 4

This energy goes into the atmosphere
The energy of the surrounding increase.
It will cause an increase in the thermal energy of its surroundings
therefore particles move faster

Question 5

What is a system

Answer 5

A system is an object or group of objects

Question 6

Example of a closed system
When do these examples become open systems

Answer 6

Toy car travelling down a lamp
A lit candle/A WAX CANDLE THAT HAS NOT BEEN LIT
Car

Stops becoming closed system
Car stops becoming a closed system when fuel is put in (increases chemical energy store)

By increasing the length of the candle (adding more wax) -increases chemical energy store of the candle)

The total amount of energy is not fixed

Question 7

What is a closed system

Answer 7

A close system is an object (or a group of objects) where the total amount of energy is fixed.

Question 8

What is the law of the conservation of Energy

Answer 8

The law of the conservation of energy states that in any system energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

Question 9

what does DISSIPATED mean

Answer 9

dissipated means wasted

Question 10

When does a closed system stop becoming a closed system?

Answer 10

A system stops becoming a closed system when energy is transferred into the system or when energy is transferred away from the system.

Question 11

How does using a low energy light bulb increase efficiency

Answer 11

A low energy light bulb increases it’s efficiency by reducing the thermal energy being produced (saves energy)

it reduces the heat energy produced

Question 12

How is an electric motor designed to be efficient

Answer 12

Electric motors are designed to be efficieint as they have been designed to produce less heat

Question 13

what can be done to objects to reduce the energy wasted and to increase efficiency,

Answer 13

to reduce the energy wasted and to increase efficiency objects can be designed to create less waste energy.

Question 14

How can the efficiency of an electric motor be increased

Answer 14

The efficiency of an electric motor can be increased by reducing friction by lubricating moving parts

Friction can be reduced by lubricating moving parts

Question 15

How can the efficiency of a house in winter be increased

Answer 15

Insulate the house to reduce the amount of heat energy lost to the outside

Question 16

Explain why the bungee jumper does not return to their original height after the jump

Answer 16

The bungee jumper doesn’t return to their original height. This is because some of the energy was transferred to the thermal energy store of the surroundings as the rope stretched and then shortened again

Question 17

How to describe the energy transfer that occurs when a person is falling and reaches the ground

Answer 17

As the person falls, their G.P.E store turns into their kinetic energy store

When the person reaches the ground, their kinetic energy store is transferred to the thermal energy store of the surroundings. Some of the dissipated energy is transferred away by sound waves to the surroundings

The air resistance acting against the falling person will cause an increase in the thermal energy store of the air (surroundings)

Question 18

What is the net change in total energy of a closed system

Answer 18

A system where neither matter nor energy can enter nor leave.

The net change in total energy in a closed system is always zero.

Question 19

what happens when you increase the energy of a particle

Answer 19

If you increase the energy of a particle, the particle will move faster

Question 20

Where is waste energy usually transferred to

Answer 20

The waste energy is transferred to useless thermal energy stores

Question 21

Describe the energy transfer that takes place when two cars collide with each other

Answer 21

As the cars collide, their kinetic energy stores turns into thermal energy store of the surroundings. Some of the energy has also been transferred away (lost) by sound waves to the surroundings

This energy enters the atmosphere causing an increase in it’s thermal energy store.

Question 22

Explain the energy transfer that takes place in a pendulum

Answer 22

At the top, the mass has the maximum store of gravitational potential energy.

As the pendulum swings down towards the centre, the gravitational potential energy store turns into kinetic energy store.
The mass has the maximum kinetic energy store at the bottom of the swing (since that is where it is moving at the fastest speed)

As the pendulum moves upwards away from the centre, the kinetic energy store turns into the gravitational potential energy store

As the pendulum swings:

Their is friction in the fixed point causing an increase in the thermal energy store of the air

The air resistance acting against the pendulum will cause an increase in the thermal energy store of the air.

Question 23

What happens when a system changes

Answer 23

When a system changes, energy is transferred. Energy can be transferred into or away from the system, between different objects in the system or between different types of energy stores.

Question 24

Explain why no device is 100% efficient

Answer 24

No device is 100% efficient as all devices produce some form of waste energy. (most often in the form of thermal energy) , so less than 100% of the input energy is transferred usefully.

Exception: Devices which function it is to produce heat are usually 100% efficient
E.g. if electric heaters produce lots of waste energy, then it isn’t really waste, and would instead count as useful output

Question 25

Explain how friction (when a car is moving) causes energy to be dissipated

Answer 25

The friction between the car’s wheels and the ground causes the kinetic energy store of the car’s wheels to be transferred to the thermal energy store of the surroundings.

Question 26

Describe the energy transfer that happens as the bungee jumper continues to fall towards the ground AND come back up to the platform

Answer 26

As the bungee jumper falls, the gravitation potential energy store turns into the kinetic energy store.

As the bungee cord stretches, the kinetic energy store turns into the elastic potential energy store

Elastic potential energy store turns into thermal energy store.

As the rope recoils and the bungee jumper rises, the thermal energy store turns into elastic potential energy store.

The elastic potential potential energy store turns into kinetic energy store.

The kinetic energy store turns into gravitational potential energy store.

The air resistance will cause an increase in the thermal energy store of the air.

Question 27

Describe the energy transfer that happens when a train uses it’s breaks to stop

Answer 27

The friction on train wheels due to the brakes reduces KE of train to zero. The kinetic energy store of the train is transferred to the thermal energy store of the surroundings. Some of the dissipated energy is transferred away by sound waves to the surroundings

Question 28

State the methods of energy transfer

Answer 28

Energy can be transferred:
Mechanically (by a force doing work)
Electrically (work done by when a current flows)
By heating
By radiation

Question 29

How to reduce unwanted energy transfers in the pendulum

Answer 29

We can reduce unwanted energy transfers by reducing friction and air resistance

Use a lubricant on the fixed point to reduce friction
Remove the air particles from around the pendulum to reduce air resistance

Question 30

What would eventually happen to the pendulum

Answer 30

As the pendulum swings:

Their is friction in the fixed point causing an increase in the thermal energy store of the air

The air resistance acting against the pendulum will cause an increase in the thermal energy store of the air.

(causing The fixed point and air around to get warmer)

Will cause the ke store turn in to thermal energy store
as thermal energy store increases, ke store decreases causing…

This will cause the pendulum to gradually swing with less energy and eventually stop