1.7 Energy, work and power EXT

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1.7a The big picture

1) Which of these household items is likely to use the least energy?

1 point

Chair

Laptop

Oven

Clear selection

2) Which of these things is likely to require the most energy?

1 point

A human running 1 kilometre

Driving a car for 10 kilometres

Launching a rocket into space

Lifting a 10 kg box above your head

Clear selection

3) As a human population, we are largely dependent on the generation of electricity. Which is not a large-scale method of producing electricity?

1 point

Coal

Electric vehicles

Natural gas

Wind turbines

Clear selection

1.7b Energy

1) Which of these statements best describes the energy transfer taking place when a ball rolls up a slope?

1 point

Gravitational potential energy to kinetic energy

Internal energy to gravitational potential energy

Kinetic energy to gravitational potential energy

Kinetic energy to internal energy

Clear selection

2) The flow diagram below shows the energy transfers for a process. Which of these processes could it be describing?

1 point

A battery powered flashlight

A battery powered toy car moving along the floor

A digital watch showing the time

A wind-up toy car moving along the floor

Clear selection

3) Complete the following sentence.

The food we eat contains a store of ………………… energy.

1 point

1.7c Energy equations

1) In order to eat fruit, a chimpanzee of mass 50kg has to climb trees to a height of 20m above the ground. Which of these is the gain in gravitational potential energy of the chimpanzee?

1 point

980J

4900J

5000J

9800J

Clear selection

2) A stone falls into a well and hits the bottom at 8.4m/s. Assuming there is no air resistance, calculate the depth of the well.

1 point

3) An apple of mass 200g falls from a tree. It hits the ground moving at 3.0m/s. Complete the following sentence.

The kinetic energy in the apple just before impact is ………………… .

1 point

1.7d Work

1) Which of the following phrases best completes this sentence?

Work is done when …

1 point

energy is transferred.

energy is used up.

a force is applied.

kinetic energy is lost.

Clear selection

2) A toy electric car has a total store of 20kJ in its batteries. When it moves forwards, friction and air resistance produces a force of 50N on the car. How far could the car travel against this force? (Assume the car motor is 100% efficient.)

1 point

0.40m

400m

1000m

1000km

Clear selection

3) The battery in an electric toy boat has a maximum capacity of 12kJ. The average force from the motor is 16N. Calculate how far the boat could travel with a full charge from the battery.

1 point

1.7e Energy resources

1) Which of these statements best describes the advantages of solar cells?

1 point

Cells are cheap and efficient

No polluting gases produced; a renewable energy resource

No polluting gases produced; cells are efficient

Renewable energy resource; cells are cheap to produce with a high output

Clear selection

2) Which of these energy resources originates from energy from the Sun?

1 point

Geothermal energy

Nuclear energy

Tidal energy

Wind energy

Clear selection

3) Identify the energy resources that do not originate from the Sun.

1 point

Nuclear, tidal and geothermal

Oil, gas and coal

Solar cells and solar panels

Wind, hydroelectric and wave

Clear selection

4) Complete the following sentence: Energy obtained from hot volcanic rocks underground is called ………………… energy.

1 point

1.7f Efficiency

1) A coal fired power station burns coal with a stored energy value of 30MJ per kilogram. If the power station is 40% efficient, how much of the original 30MJ is converted to electrical energy?

1 point

0.75MJ

12MJ

75MJ

1200MJ

Clear selection

2) a) An escalator is a moving staircase which takes people up one floor in a building. During normal operation, the ………………… energy output is gravitational potential energy and …

1 point

2) b) … and the ………………… energy output is internal energy.

1 point

3) A water pump has an efficiency of 65%. When it is operated for one minute, 11J is wasted as internal energy and 10J is wasted as sound waves. No more energy is wasted.

Calculate how much electrical work is done on the pump in one minute.

1 point

1.7g Power

1) Which of these statements best describes the quantity 'power'?

1 point

The energy transferred into useful work

The energy transferred per unit time 𝑡

The time taken for the energy to be transferred

The total energy transferred

Clear selection

2) An electric kettle is rated as 2.0kW. How many joules of energy can be transferred in 1.0 minute?

1 point

3) A car of mass 550kg is accelerating up a hill from rest. After 10s, the car has gained a vertical height of 3.5m and is moving at 6.0m/s.

Calculate the power output of the engine.

Give your answer to three significant figures and include the unit.

1 point

1.7h Practical Find your power

1) True or false? Power is defined as work done per unit time and as the energy transferred per unit time.

1 point

2) You measured the height of the stairs incorrectly during your practical and recorded them to be higher than they are. Identify the effect this would have on your power calculations.

1 point

None

Over-estimate the power in your legs

Over-estimate the power in your arms

Under-estimate the power in your legs

Clear selection

3) a) Complete the following sentence.

When lifting the dumbbells, if you complete twice as many lifts but take three times longer, you have done ………………… work and …

1 point

3) b) … and used ………………… power.

1 point

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