Work done occurs when an object is moved over a distance by a force applied in the direction of its displacement.

What happens to an object's energy if a force acts in the same direction as its motion?

The object gains energy , usually to its kinetic energy store.

What happens to an object's energy if a force acts in the opposite direction to its motion?

The object loses energy , which is dissipated to the surroundings, usually by heating .

The work done equation is W = F × ______ , where the missing quantity is the distance moved in the direction of the force.

The work done equation is W = F × d , where the missing quantity is the distance moved in the direction of the force.

In which two units can work done be measured?

Joules (J) or newton-metres (N m) .

True or False? If a force is applied to an object but no movement results, work is done.

False. No work is done unless the force causes the object to move .

Define gravitational potential energy (GPE) .

The energy an object has due to its height in a gravitational field.

If an object falls, energy is transferred ______ from its gravitational potential store.

If an object falls, energy is transferred away from its gravitational potential store.

How does the Moon's gravitational field strength compare to Earth's, and what effect does this have on lifting a mass?

The Moon's gravitational field strength is less than Earth's, so it is easier to lift a mass on the Moon.

True or False? Gravitational field strength on the surface of a gas giant such as Jupiter is less than on Earth.

False. Gravitational field strength on gas giants such as Jupiter is more than on Earth, making it harder to lift a mass there.

Define kinetic energy .

The amount of energy an object has as a result of its mass and speed .

In the kinetic energy equation, the speed of the object must be ______ , not simply multiplied by the mass.

In the kinetic energy equation, the speed of the object must be squared , not simply multiplied by the mass.

Does the amount of kinetic energy an object has depend on its direction of motion?

No. Kinetic energy depends only on speed , not direction, since only the magnitude of v is squared in the equation.

True or False? A stationary object has energy in its kinetic energy store.

False. An object must be in motion to have energy in its kinetic energy store; a stationary object has none.

In a swinging pendulum, energy is transferred back and forth between which two energy stores?

The kinetic energy store and the gravitational potential energy store.

Define a perfect energy transfer .

An energy transfer in which there is no wasted energy ; it is assumed when the wasted energy transfer is negligible , for example when air resistance is ignored.

For a pendulum, assuming a perfect energy transfer, total kinetic energy equals total ______ energy.

For a pendulum, assuming a perfect energy transfer, total kinetic energy equals total gravitational potential energy.

True or False? A perfectly efficient energy transfer with zero wasted energy is possible in reality.

False. There is no such thing as a truly perfect energy transfer in reality; it is only an assumption made when the wasted energy is negligible.

Power is the rate of doing work , or equivalently the rate of transfer of energy (energy transferred per unit time).

Define power rating .

The power rating of an appliance is the amount of energy it transfers per unit time, often given in watts (W), kilowatts (kW) or megawatts (MW). 1 kW = 1000 W and 1 MW = 1 000 000 W.

Two electric motors lift the same weight through the same height, but motor A does this in less time than motor B. Which motor has the greater power, and why?

Motor A has the greater power, because it transfers the same amount of energy (does the same work) in a shorter time .

The SI unit of power is the ______ .

The SI unit of power is the watt (W).

True or False? A higher power rating always means an appliance transfers more total energy than a lower-power one.

False. Power is the rate of energy transfer — the total energy transferred also depends on how long the appliance is used, so a lower-power appliance used for longer can transfer more total energy.

Define energy resource .

An energy resource is a large store of energy that can be used to generate electricity and to heat homes and businesses.

Define renewable energy resource.

A renewable energy resource is one that is replenished at a faster rate than the rate at which it is being used, so it will not run out.

Name the six renewable energy resources described in this note.

Solar energy, wind , bio-fuel , hydroelectricity , geothermal and tidal .

Name the two types of non-renewable energy resource.

Fossil fuels (coal, oil and natural gas) and nuclear fuel .

Describe the basic process by which most energy resources are used to generate electricity.

A turbine is turned (often by steam or moving water), which turns a generator , generating electricity that is transferred electrically to the National Grid.

In a fossil fuel power station, energy is transferred from the chemical store of the fuel to the ______ store of the water, which produces the steam that turns the turbine.

In a fossil fuel power station, energy is transferred from the chemical store of the fuel to the thermal store of the water, which produces the steam that turns the turbine.

Describe the energy transfer chain when a wind turbine generates electricity for the National Grid.

Kinetic store of the wind → kinetic store of the turbine → kinetic store of the generator → transferred electrically to the National Grid.

True or False? Nuclear power stations generate electricity using steam to turn turbines, in a similar way to fossil fuel power stations.

True. In both cases, water is heated to produce steam which turns a turbine connected to a generator — the difference is that the energy originates in the nuclear store of the fuel rather than its chemical store .

Define a reliable energy resource.

A reliable energy resource is one that can produce energy at any time. A non-reliable resource can only produce energy some of the time (e.g. when it is windy).

Define a renewable energy resource.

A renewable energy resource is one that is replenished at a faster rate than the rate at which it is being used, so it will not run out.

Give one advantage and one disadvantage of nuclear power as an energy resource.

Advantages include: reliable; produces large amounts of energy consistently; produces no pollution or CO 2 ; large amounts of energy from small amounts of fuel. Disadvantages include: produces radioactive waste that takes thousands of years to decay; expensive and slow to build and maintain; cannot respond quickly to changes in demand.

Give one advantage and one disadvantage of using fossil fuels to generate electricity.

Advantage: reliable — can produce large amounts of energy consistently and respond to changes in demand. Disadvantage: produces carbon dioxide (CO 2 ), which contributes to global warming, and sulphur dioxide, which causes acid rain.

Wind power produces no pollution and has low running costs once built. Why is it still considered non-reliable?

Because it can only generate electricity when the wind is blowing (in a suitable direction) — it cannot produce energy on demand at any time.

Give one advantage and one disadvantage of tidal power.

Advantage: tides are very predictable , so energy can be produced at regular intervals. Disadvantage: there are few suitable locations (estuaries), and it can harm aquatic life and disrupt shipping.

Wind power produces no pollution or ______ , though it is non-reliable as it only generates electricity when the wind is blowing.

Wind power produces no pollution or carbon dioxide (CO~2~) , though it is non-reliable as it only generates electricity when the wind is blowing.

True or False? Hydroelectric power produces no pollution or carbon dioxide under all circumstances.

False. It produces no pollution or CO 2 unless a pump is used to return the water to a height, since this uses fossil fuels.

IGCSEPhysicsEdexcelPhysics (Modular)Unit 1Flashcards3. Energy Resources & Energy TransfersWork, Power & Energy Resources

Work, Power & Energy Resources (Edexcel IGCSE Physics (Modular): Unit 1): Flashcards

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Cards in this collection (48)

Define work done.
Work done occurs when an object is moved over a distance by a force applied in the direction of its displacement.
What happens to an object's energy if a force acts in the same direction as its motion?
The object gains energy, usually to its kinetic energy store.
What happens to an object's energy if a force acts in the opposite direction to its motion?
The object loses energy, which is dissipated to the surroundings, usually by heating.
The work done equation is W = F × ______, where the missing quantity is the distance moved in the direction of the force.
The work done equation is W = F × d, where the missing quantity is the distance moved in the direction of the force.
In which two units can work done be measured?
Joules (J) or newton-metres (N m).
A car's brakes apply a force of 500 N and bring it to a stop after 23 m. Calculate the work done by the brakes.
$W = F \times d = 500 \times 23 = 11500 J$
True or False?
If a force is applied to an object but no movement results, work is done.
False.
No work is done unless the force causes the object to move.
Define gravitational potential energy (GPE).
The energy an object has due to its height in a gravitational field.
If an object falls, energy is transferred ______ from its gravitational potential store.
If an object falls, energy is transferred away from its gravitational potential store.
State the equation for gravitational potential energy, defining each symbol.
$G P E = m \times g \times h$
Where m = mass (kg), g = gravitational field strength (N/kg), h = height (m), and GPE is in joules (J).
What is the approximate gravitational field strength, g, at the Earth's surface?
10 N/kg.
How does the Moon's gravitational field strength compare to Earth's, and what effect does this have on lifting a mass?
The Moon's gravitational field strength is less than Earth's, so it is easier to lift a mass on the Moon.
A man of mass 70 kg climbs a flight of stairs 3 m higher than the floor (g = 10 N/kg). Calculate the increase in his gravitational potential energy.
$G P E = m \times g \times h = 70 \times 10 \times 3 = 2100 J$
True or False?
Gravitational field strength on the surface of a gas giant such as Jupiter is less than on Earth.
False.
Gravitational field strength on gas giants such as Jupiter is more than on Earth, making it harder to lift a mass there.
Define kinetic energy.
The amount of energy an object has as a result of its mass and speed.
State the equation for kinetic energy, defining each symbol.
$K E = \frac{1}{2} \times m \times v^{2}$
Where m = mass (kg), v = speed (m/s), and KE is in joules (J).
In the kinetic energy equation, the speed of the object must be ______, not simply multiplied by the mass.
In the kinetic energy equation, the speed of the object must be squared, not simply multiplied by the mass.
Calculate the kinetic energy of a vehicle of mass 1200 kg moving at a speed of 27 m/s. Give your answer to 2 significant figures.
$K E = \frac{1}{2} \times 1200 \times 27^{2} = 437400 J \approx 440000 J$
Does the amount of kinetic energy an object has depend on its direction of motion?
No. Kinetic energy depends only on speed, not direction, since only the magnitude of v is squared in the equation.
True or False?
A stationary object has energy in its kinetic energy store.
False.
An object must be in motion to have energy in its kinetic energy store; a stationary object has none.
In a swinging pendulum, energy is transferred back and forth between which two energy stores?
The kinetic energy store and the gravitational potential energy store.
Define a perfect energy transfer.
An energy transfer in which there is no wasted energy; it is assumed when the wasted energy transfer is negligible, for example when air resistance is ignored.
For a pendulum, assuming a perfect energy transfer, total kinetic energy equals total ______ energy.
For a pendulum, assuming a perfect energy transfer, total kinetic energy equals total gravitational potential energy.
A rollercoaster of mass 100 kg starts at a height of 15 m and reaches ground level, with frictional effects ignored (g = 10 N/kg). Calculate its maximum speed at ground level.
$Δ G P E = m \times g \times Δ h = 100 \times 10 \times 15 = 15000 J$
$Δ G P E = K E (perfect transfer)$
$v = \sqrt{\frac{2 \times K E}{m}} = \sqrt{\frac{2 \times 15000}{100}} = 17 m/s$
True or False?
A perfectly efficient energy transfer with zero wasted energy is possible in reality.
False.
There is no such thing as a truly perfect energy transfer in reality; it is only an assumption made when the wasted energy is negligible.
Define power.
Power is the rate of doing work, or equivalently the rate of transfer of energy (energy transferred per unit time).
Define power rating.
The power rating of an appliance is the amount of energy it transfers per unit time, often given in watts (W), kilowatts (kW) or megawatts (MW). 1 kW = 1000 W and 1 MW = 1 000 000 W.
State the equation linking power, work done and time.
$P = \frac{W}{t}$ where P = power (W), W = work done (J), t = time (s).
Two electric motors lift the same weight through the same height, but motor A does this in less time than motor B. Which motor has the greater power, and why?
Motor A has the greater power, because it transfers the same amount of energy (does the same work) in a shorter time.
The SI unit of power is the ______.
The SI unit of power is the watt (W).
An iron of power 2000 W is used for 5 minutes. Calculate the work done.
Time in seconds: t = 5 × 60 = 300 s.
$W = P t = 2000 \times 300 = 600 000 J$
True or False?
A higher power rating always means an appliance transfers more total energy than a lower-power one.
False.
Power is the rate of energy transfer — the total energy transferred also depends on how long the appliance is used, so a lower-power appliance used for longer can transfer more total energy.
Define energy resource.
An energy resource is a large store of energy that can be used to generate electricity and to heat homes and businesses.
Define renewable energy resource.
A renewable energy resource is one that is replenished at a faster rate than the rate at which it is being used, so it will not run out.
Name the six renewable energy resources described in this note.
Solar energy, wind, bio-fuel, hydroelectricity, geothermal and tidal.
Name the two types of non-renewable energy resource.
Fossil fuels (coal, oil and natural gas) and nuclear fuel.
Describe the basic process by which most energy resources are used to generate electricity.
A turbine is turned (often by steam or moving water), which turns a generator, generating electricity that is transferred electrically to the National Grid.
In a fossil fuel power station, energy is transferred from the chemical store of the fuel to the ______ store of the water, which produces the steam that turns the turbine.
In a fossil fuel power station, energy is transferred from the chemical store of the fuel to the thermal store of the water, which produces the steam that turns the turbine.
Describe the energy transfer chain when a wind turbine generates electricity for the National Grid.
Kinetic store of the wind → kinetic store of the turbine → kinetic store of the generator → transferred electrically to the National Grid.
True or False?
Nuclear power stations generate electricity using steam to turn turbines, in a similar way to fossil fuel power stations.
True.
In both cases, water is heated to produce steam which turns a turbine connected to a generator — the difference is that the energy originates in the nuclear store of the fuel rather than its chemical store.
Define a reliable energy resource.
A reliable energy resource is one that can produce energy at any time. A non-reliable resource can only produce energy some of the time (e.g. when it is windy).
Define a renewable energy resource.
A renewable energy resource is one that is replenished at a faster rate than the rate at which it is being used, so it will not run out.
Give one advantage and one disadvantage of nuclear power as an energy resource.
Advantages include: reliable; produces large amounts of energy consistently; produces no pollution or CO₂; large amounts of energy from small amounts of fuel.
Disadvantages include: produces radioactive waste that takes thousands of years to decay; expensive and slow to build and maintain; cannot respond quickly to changes in demand.
Give one advantage and one disadvantage of using fossil fuels to generate electricity.
Advantage: reliable — can produce large amounts of energy consistently and respond to changes in demand.
Disadvantage: produces carbon dioxide (CO₂), which contributes to global warming, and sulphur dioxide, which causes acid rain.
Wind power produces no pollution and has low running costs once built. Why is it still considered non-reliable?
Because it can only generate electricity when the wind is blowing (in a suitable direction) — it cannot produce energy on demand at any time.
Give one advantage and one disadvantage of tidal power.
Advantage: tides are very predictable, so energy can be produced at regular intervals.
Disadvantage: there are few suitable locations (estuaries), and it can harm aquatic life and disrupt shipping.
Wind power produces no pollution or ______, though it is non-reliable as it only generates electricity when the wind is blowing.
Wind power produces no pollution or carbon dioxide (CO~2~), though it is non-reliable as it only generates electricity when the wind is blowing.
True or False?
Hydroelectric power produces no pollution or carbon dioxide under all circumstances.
False.
It produces no pollution or CO₂ unless a pump is used to return the water to a height, since this uses fossil fuels.

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