Work Energy Power

Question 1

What is work done?

Answer 1

Work done by a force on an object is the product of the force and the distance moved by the object in the direction of gather force. Energy is converted from one form to another when work is done.

Question 2

What is the formula is work done?

Answer 2

Work done= Force X Distance moved in the direction of the force

Question 3

What is the SI unit of work?

Answer 3

Joule (J)

Question 4

What is chemical potential energy?

Answer 4

Chemical potential energy is potential energy stored in food (released by respiration) or fuels like petrol or diesel (released by combustion/burning). Batteries and cells also have chemical potential energy which can be changed into electrical energy.

Question 5

What is the energy conversion of the burning of fossil fuels?

Answer 5

Chemical potential energy—> Heat energy—> Kinetic energy—> Electrical energy

Question 6

Is nuclear energy renewable?

Answer 6

No Nuclear energy is usually considered another non-renewable energy source. Although nuclear energy itself is a renewable energy source, the material used in nuclear power plants is not.

Question 7

What is the formula of gravitational potential energy (GPE)?

Answer 7

GPE (J)= mass (kg) x gravitational field strength (N/kg) x height (m)

Mass (kg) x gravitational field strength (N/kg)= weight (N)

Question 8

When does elastic potential energy?

Answer 8

Elastic potential energy is the potential energy an object has when it is stretched or compressed.

Question 9

What is kinetic energy and what makes kinetic energy increases?

Answer 9

Kinetic energy is the energy a body has due to its motion. The greater the mass of the object and the faster it is moving, the greater its kinetic energy.

Question 10

What is the law of conservation of energy?

Answer 10

The law of conservation of energy states that energy can only change from one form into another, but cannot be created or destroyed. The total amount of energy in any isolated system must remain constant.

Question 11

What is light energy?

Answer 11

Light energy is the energy that enables us to see. Bodies that are luminous give out light energy.

Question 12

What is sound energy?

Answer 12

Sound energy is produced when object vibrates. Sound enables us to communicate and listen to music.

Question 13

What is power?

Answer 13

Power is the rate of work done or rate of energy conversion.

Question 14

What is the formula of power?

Answer 14

Power= Work done/time taken or Energy converted/ time taken

Question 15

What is the SI unit of power?

Answer 15

Watt(W)

Question 16

1W is defined as the rate of work done or energy conversion of ___ joule per ____.

Answer 16

1 joule per second. 1W=1J/s

Question 17

A boy is blowing air into a balloon to inflate it. Describe the energy conversion during the process.

Answer 17

The chemical potential energy stored in the boy’s body is converted to kinetic energy which pushes air into the balloon and is converted to elastic potential energy which stretches the balloon.

Question 18

What is the first step that you should do when you see this type of question: A box of weight 200N is pulled 6.00m along a horizontsal floor by a force of 10.0N. It is then lifted vertically though a distance of 2.00m at constant speed.
What is the work done against graviational force?

Answer 18

The first step you should do is to draw the diagram out to visualise it better. Then, add the arrows for the object. For example: If the weight of the box is 200N, draw an aroow downwards. This reminds you that both arrows for the force and the distance are suppose to be either horizontal, vertical or slanted. The ans is 400 J

Question 19

Which is not a renewable source of energy?
A coal
B hydroelectricity
C sunlight
D wind

Answer 19

A coal is a type of fossil fuels and fossil fuels are not a renewable source of energy.

Question 20

Wha are some examples of fossil fuels?

Answer 20

Some example of fossil fuels include crude oil, natural gas and coal.

Question 21

As fossil fuels are burnt, what happens?

Answer 21

As fossil fuels are burnt, the carbon dioxide (greenhouse) produces traps heat from the sun in the earth’s atmosphere. This causes global warming.

Question 22

Which statements are correct?
1 Hydroelectric energy converts kinetic energy to electric energy/
2 Nuclear energy is a renewable source of energy.
3 Since ethanol is made from glucose produced in plants, it is a renewable fuel.
A 1 only
B 1 and 3 only
C 2 and 3 only
D 1,2 and 3

Answer 22

B
Nuclear energy is not renewable source of energy (Uranium is not renewable)
Statement 3 biofuel—> renewable
Non renewable are coal, fossil fuels

Question 23

How do you calculate the velocity of an object at let’s say point B of a roller coaster when you are given the height of point B, and height of point A where the object is at rest. You are not given the mass of the object.

Answer 23

mghA + KE at A (1/2 x mass x velocity square)= mghB + KE at B (1/2 x mass x velocity square)
Cancel out B
Let’s say height at A is 40.0m
40 x (g) + 0= height at B (22.0) x (g) + 1/2 velocity square at B
Calculate to get the answer

Question 24

What are the five renewable sources of energy?

Answer 24

Biofuels
Geothermal
Hydroelectric
Solar
Wind

Question 25

What is biofuels and what are the advantages and disadvantages?

Answer 25

Biofuels are fuels derived from animal and plant matter such as water hyacinth and sugar cane. They are also used for motor vehicles. Carbon dioxide is produce with similar contribution to the heat trapped in the earths atmosphere. However, the plants that produce these biofuels take in carbon dioxide during photosynthesis and will partially offset the contribution to the trapping of heat in atmosphere.

Question 26

What is geothermal and what are the advantages and disadvantages?

Answer 26

Geothermal
Geothermal energy has been used for thousands of years in some countries for
cooking and heating. It is simply power derived from the Earth’s internal heat.
This thermal energy is contained in the rock and fluids beneath Earth’s crust. These
underground reservoirs of steam and hot water can be tapped to generate electricity
or to heat and cool buildings directly.
A geothermal heat pump system can take advantage of the constant temperature of
the upper ten feet (three meters) of the Earth’s surface to heat a home in the winter.

Disadvantages:
Because material from underground is extracted, the land around these geothermal
power stations may sink, causing damage to the buildings and roads. The flow patterns
of rainwater may also be significantly affected.

Question 27

What is hydroelectric and the advantages and disadvantages?

Answer 27

Hydroelectric
Flow of water from the reservoir turns the blades of a turbine to generate electrical
energy.
Advantage: The power stations do not produce pollutants.

Disadvantages
However, the damming of the
river can cause extensive flooring in large areas of forest, affecting the ecosystems
around the power stations.

Question 28

What is solar energy and its advantage and disadvantage

Answer 28

Energy in the sunlight can be directly converted into electrical energy by solar cells. Solar energy can be used to heat water to drive a turbine to generate electrical energy.
Advantage: No harmful substances or pollutants are produced when solar cells generate electricity.
Potential disadvantage that is not written in the notes: the high initial cost of these solar panels

Question 29

What is wind energy and its advantages and disadvantages?

Answer 29

Advantage: Wind energy provides electrical energy for household and research stations.
Disadvantage: However, wind blades may cause a significant number of death of birds.