physics chapter 6

Question 1

what is energy

Answer 1

energy is the capacity to do work and is measured in joules

Question 2

what is the unit that is used for energy

Answer 2

the joule (J) is a commonly used unit of energy

Question 2

what are the different types of energy transfers

Answer 2

• by heating
• by forces
• by electric currents
• by electromagnetic waves
• by sound waves

Question 2

what are the different stores of energy

Answer 2

• kinetic
• elastic
• gravitational potential
• electrostatic
• chemical
• internal
• nuclear

Question 2

how do we calculate the amount of energy that the body has

Answer 2

kinetic energy ( in joules ) = 1/2 ( mass of the body x speed of the body ^2)

Ek = 1/2 ( mv^2)

Question 3

what are some examples of the use of principle of conservation of energy

Answer 3

• an ideal pendulum swinging
• a robot waiter on the move
• hammering nail

Question 3

how useful is fossil fuel store and how is it produced

Answer 3

• examples of fossil fuels are petroleum, natural gas, coal and wood
• when a fuel is burnt in air, for cooking food ina pot, heating transfers energy from the chemical store of the fuel to the thermal stores of the pot, the food and the surroundings

Question 3

how do we calculate the size of the gravitational potential store of a body at a height above ground

Answer 3

gravitational potential energy = mass of the body x gravitational field strength x height

Ep = mgh

Question 3

what is the principle of conservation of energy

Answer 3

the principle of conservation of energy states that energy cannot be created or destroyed. it can only be transferred from one energy to another. the total amount of energy in the different energy stores before and after a process must be the same

Question 3

what is a common unit used to measure the unit of work

Answer 3

joules ( j )

Question 3

how can we calculate the work done by a constant force

Answer 3

work done by a constant force = constant force x distance moved by the object in the direction of the force

w = fd

Question 4

define work done

Answer 4

work done by a constant force on an object is the force and distance moved by the object in the direction of a force

Question 4

what are the disadvantages of biofuels

Answer 4

Environmental pollution from the gases produced during burning contributes to global warming

Question 4

what are the different examples of major energy resources

Answer 4

• fossil fuels
• biofuels
• hydropower
• geothermal resources
• solar power
• nuclear power

Question 4

what are the advantages of fossil fuels

Answer 4

• widely available at a large scale
• relatively cheaper in cost of production

Question 4

what are the disadvantages of fossil fuels

Answer 4

environmental pollution from the gases, produced during burning, contributes to global warming

Question 4

what are the advantages of biofuels

Answer 4

• Widely available at a large scale
• Relatively cheaper in cost of production

Question 5

how useful is biofuel store and how is it produced

Answer 5

• Examples of biofuels are ethanol, biodiesel and biogas, which are derived from biomass. Biomass comes from living materials such as corn, sugar cane, vegetable oils, animal fats and animal manure.
• Biofuels have chemical stores of energy.
• Heating transfers energy from the chemical store of biofuels to the thermal store of food or water during cooking or boiling.

Question 5

how useful is hydropower store and how is it produced

Answer 5

• Water movement provides a kinetic store of energy to generate electrical power. This hydropower or water power can be obtained from ocean waves, tides and water behind hydroelectric dams.
• Water behind hydroelectric dams has gravitational potential store of energy. This energy in the gravitational potential store is transferred mechanically to the kinetic store by releasing the water and letting it flow downwards. The flowing water will cause the turbines to spin.
• As the turbines spin, the kinetic store of energy of the turbines is transferred by electric current to factories and homes.

Question 6

what are the advantages of hydropower

Answer 6

• Clean method of producing cheap electricity
• Renewable energy resource as the water movement can be continually regenerated

Question 7

what are the disadvantages of hydropower

Answer 7

• High cost of building dams, turbines and generators
• Damming a river for hydroelectric power station may cause damage to the environment surrounding the river

Question 8

how useful is geothermal resource store and how is it produced

Answer 8

• In certain areas, such as volcanic regions, geological forces push large amounts of hot molten rocks near the Earth’s surface. These places are known as geothermal hotspots.
• Water that makes its way to these geothermal hotspots is heated and subjected to great pressure.
• This heated water has a large thermal store of energy. It is forced to the surface as boiling water and steam to drive turbines to generate electrical power

Question 9

what are the advantages of geothermal resources

Answer 9

• Clean source of naturally available thermal energy
• Renewable energy resource

Question 10

what are the disadvantages of geothermal resources

Answer 10

• Environmental pollution caused by the release of poisonous gases such as hydrogen sulphide into the atmosphere
• Not widely available as they are found only in certain areas around the world

Question 11

how useful is solar power store and how is it produced

Answer 11

* © Solar power comes from the Sun. The Sun has a nuclear store of energy by nuclear fusion, where hydrogen atoms combine to form helium atoms. * The energy in the nuclear store of the Sun is transterred by infrared electromagnetic waves to the thermal store of a solar panel for heating water. * Solar power from the Sun is the source of wind power. The uneven heating of the Earth's surfaces (land, sea and air) results in the movement of warm and cold air. This produces wind. By means of wind electric generators, energy from the kinetic store of the wind is transferred electrically to the chemical store of factories and homes for useful purposes.

Question 12

what are the advantages of solar power

Answer 12

* Less polluting than fossil fuels * Renewable energy resource

Question 13

what are the disadvantages of solar power

Answer 13

* Not always available as there is no sunlight at night, and it is weather-dependent * Uses a lot of space

Question 14

how useful is nuclear power store and how is it produced

Answer 14

* Energy from the nuclear store in nuclear fuels, such as uranium, can be transferred to large thermal sources to heat up water into steam. * Electrical power is generated when steam drives the turbines in a nuclear power station.

Question 15

what are the advantages of nuclear power

Answer 15

* Higher reliability in supplying uninterrupted power

Question 16

what are the disadvantages of nuclear power

Answer 16

* Risk of accidents and pollution from the improper disposal of radioactive wastes * Non-renewable energy resource as the amount of nuclear fuel is limited

Question 17

what is power

Answer 17

power is defined as the work done or energy transferred per unit time

Question 18

what is the common unit used for power

Answer 18

watt (W)

Question 19

how do we calculate the power

Answer 19

Power ( in W ) = work done / time taken