Energy, work and power

A worker in a factory must raise a box onto a shelf. Which action would mean the worker does the smallest amount of work?

Feb/March 2016

Which of the following is a non-renewable energy resource?

Feb/March 2016

A weight-lifter lifts a $2000\ \text{N}$ load by a vertical distance of $2.0\ \text{m}$ in $0.80\ \text{s}$. What useful power is developed in this action?

Feb/March 2016

A wind turbine produces $54\ \text{kW}$ of useful power from an input of $180\ \text{kW}$ of wind power. Which calculation shows the percentage efficiency of the turbine?

Feb/March 2016

The table lists four energy sources and shows whether the source’s energy comes from the Sun. Which row is correct?

Feb/March 2016

Fig. 5.1 illustrates a wave-powered generator that converts the motion of sea waves into electricity. The diagram labels these parts: chamber, incoming waves, air, turbine and generator, with the waves causing the water to rise and fall.

Feb/March 2016

On Fig. 3.1, sketch a graph of extension against load for a spring that follows Hooke’s law.

Feb/March 2016

A motor vehicle engine produces a large amount of power. Which statement is correct?

Feb/March 2017

An air-conditioning unit, a lamp and an electric fire each take electrical energy from the mains supply. Which of these devices has all of that energy ultimately passed on to the surroundings?

Feb/March 2017

A man has a choice of using either an escalator or a lift to move upwards between two floors in a hotel. The escalator takes $20\,\text{s}$ to transport the man from one floor to the other. The useful work done against gravity is $W$. The useful power developed is $P$. The lift takes $30\,\text{s}$ to transport the same man between the same two floors. What useful work against gravity is done by the lift, and what useful power is developed by the lift?

Feb/March 2017

A $40\,\text{W}$ lamp loses $34\,\text{J}$ of energy each second as heat to its surroundings. What efficiency does the lamp have?

Feb/March 2017

An air-conditioning unit, a lamp and an electric fire each take electrical energy from the mains supply. For which one of these devices is all of this energy ultimately passed to the surroundings?

Feb/March 2017

To move between two floors in a hotel, a man may use either an escalator or a lift. The escalator needs 20 seconds to take the man from one floor to the other. The useful work done against gravity is $W$. The useful power developed is $P$. The lift needs 30 seconds to take the same man between the same two floors. What useful work against gravity does the lift do, and what useful power does the lift develop?

Feb/March 2017

A ball is stationary at the top of a hill. It rolls down the hill. At the bottom of the hill, the ball collides with a wall and comes to rest. Which energy changes occur?

Feb/March 2018

A man hauls a truck through a distance of $20\,\text{m}$, as illustrated in the three diagrams. Which statement about the work done against gravity is correct?

Feb/March 2018

A ball is stationary at the summit of a hill. It then rolls downhill. When it reaches the bottom of the hill, the ball strikes a wall and comes to rest. Which energy changes take place?

Feb/March 2018

A student rides a bicycle on a level road at a speed of $5.0\,\text{m s}^{-1}$. The combined mass of the student and bicycle is $120\,\text{kg}$. The student uses the brakes and comes to rest. The braking distance is $10\,\text{m}$. What is the average braking force?

Feb/March 2018

Fig. 4.1 illustrates a hydroelectric system that generates electrical energy. The labels shown are reservoir, pipe, power station and water.

Feb/March 2018

Explain why the object’s gravitational potential energy (g.p.e.) increases.

Feb/March 2018

Which source of energy generates electrical energy by producing steam?

Feb/March 2019

What unit is used for power?

Feb/March 2019

A car with mass $1500\,\text{kg}$ is travelling at $20\,\text{m s}^{-1}$. It then speeds up until its velocity reaches $25\,\text{m s}^{-1}$. What is the increase in the car’s kinetic energy?

Feb/March 2019

Which source of energy generates electrical energy by making steam?

Feb/March 2019

A car moving along a straight, level road has $1.6\,\text{MJ}$ of kinetic energy. It speeds up for $20\,\text{s}$ until its kinetic energy becomes $2.5\,\text{MJ}$. What average power output is needed to raise the car’s kinetic energy?

Feb/March 2019

Fig. 4.1 shows a truck raising a heavy load.

Feb/March 2019

Fig. 5.1 depicts part of a solar farm, where the solar panels can tilt and turn.

Feb/March 2019

State one advantage and one disadvantage of using a wind turbine as a source of electrical energy.

Feb/March 2019

Which row gives one advantage and one disadvantage of wind turbines?

Feb/March 2020

A box with mass $m$ and weight $W$ is taken up a flight of stairs whose total height is $x$ and whose total width is $y$. Which quantities determine the work done against gravity on the box?

Feb/March 2020

A ball is let go from rest and rolls down a track from the position shown. Which is the farthest point that the ball can possibly reach?

Feb/March 2020

Which row identifies one advantage and one disadvantage of wind turbines?

Feb/March 2020

An electric motor delivers $900\,\text{J}$ of useful output energy. Its efficiency is $60\%$. What electrical energy is provided to the motor?

Feb/March 2020

It takes a crane $2.0\,\text{minutes}$ to raise a $500\,\text{kg}$ load to the roof of a building that is $12\,\text{m}$ high. Calculate the useful power developed against gravity by the crane.

Feb/March 2020

Fig. 5.1 illustrates a wind turbine.

Feb/March 2020

Fig. 3.1 presents a model wind turbine that is used to show how wind energy can be converted into electricity. The wind is shown blowing towards the model.

Feb/March 2020

A horizontal force drags a box across a level surface. The box gains $30\,\text{J}$ of kinetic energy and friction between the box and the surface generates $10\,\text{J}$ of thermal energy. How much work is done by the force?

Feb/March 2021

The table gives the work done and the time spent by four machines. Which machine is the most powerful?

Feb/March 2021

Which energy source is used to heat water until it boils and produces steam in power stations?

Feb/March 2021

A box is pulled along a horizontal surface by a horizontal force. The box gains $30\,\text{J}$ of kinetic energy, and friction between the box and the surface generates $10\,\text{J}$ of thermal energy. How much work is done by the force?

Feb/March 2021

A crane is used to lift loads in the vertical direction. The crane's output power for lifting a car is $P$. The crane then lifts a lorry, which has $3.0$ times the weight of the car, through $0.25$ of the distance in $0.50$ of the time. What is the output power of the crane now?

Feb/March 2021

Fig. 4.1 presents a simple diagram of the principal components in a geothermal power station used to produce electricity. Several components on the station are labelled. The labels shown include: steam; electrical energy; cooling station; production well; injection well; hot water/steam; hot rocks; water.

Feb/March 2021

A power station uses waste matter from farm crops to produce electricity.

Feb/March 2021

Which power station causes the highest atmospheric pollution per unit of energy generated?

Feb/March 2023

A $500\,\text{N}$ weight is lifted through a vertical distance of $5\,\text{cm}$. What amount of work is done by the force?

Feb/March 2023

Which unit is used for power?

Feb/March 2023

The relationship for determining the change in gravitational potential energy of an object is $\Delta E_p = Y \times Z \times \Delta h$, with $\Delta E_p$ representing the change in gravitational energy and $\Delta h$ representing the change in height. Which row identifies the quantities $Y$ and $Z$?

Feb/March 2023

A machine takes in $200\ \text{W}$ of power and produces a useful output energy of $1\ \text{kJ}$ in $6$ minutes. What is the machine’s efficiency?

Feb/March 2023

State the unit used for power.

Feb/March 2023

This question concerns work, energy stores and energy transfers.

Feb/March 2023

State the law of conservation of energy.

Feb/March 2023

Three situations are given. 1 a person inflating a party balloon by blowing air into it 2 a crane raising a block of concrete 3 a stack of books at rest on a shelf. In which situations is work being done?

Feb/March 2024

Which row identifies an advantage and a disadvantage of wind turbines?

Feb/March 2024

A ball is dropping toward the ground. Which transfer between energy stores is occurring?

Feb/March 2024

Fig. 4.1 shows a student operating a battery-powered device.

Feb/March 2024

Which equation links the work done $W$ on an object by a force $F$ when it moves through a distance $d$?

Feb/March 2025

A boy has an average useful power output of $60\,\text{W}$ while he rides his bicycle for $2.0\,\text{minutes}$. What useful energy is transferred?

Feb/March 2025

A resistor carries a current $I$. The potential difference (p.d.) across it is $V$. What quantity is given by the product $IV$?

Feb/March 2025

Which resource does not have the Sun as its main source of energy?

Feb/March 2025

Four students work out the efficiency of four different electrical devices. The teacher knows that one student has made an error in the calculation. Which efficiency value is incorrect?

Feb/March 2025

A car is moving at $8.0\,\text{m s}^{-1}$. Its kinetic energy is $32\,000\,\text{J}$. What is the kinetic energy of the car when its speed rises to $16\,\text{m s}^{-1}$?

Feb/March 2025

A power station burns biofuels to produce electrical power.

Feb/March 2025

An electric motor is used to raise a load, as illustrated in Fig. 5.1.

Feb/March 2025

A coal-fired power station produces electricity. The coal is burned, and the energy given out is used to heat water until it boils. The steam from the water causes the generator to rotate, which produces electricity. What terms describe the energy stored in the coal and the energy of the generator when it is moving?

May/June 2016

Four different children each run up the same staircase. Which child has the greatest useful power when climbing the stairs?

May/June 2016

A skier travels from the base of a ski slope to the summit and increases her gravitational potential energy by $10\,000\,\text{J}$. She then goes back down the slope. When she reaches the bottom, her kinetic energy is $2000\,\text{J}$. How much energy is dissipated in overcoming friction and air resistance during the descent?

May/June 2016

Which energy source is used to heat water until it becomes steam in power stations?

May/June 2016

Inside a factory, two men X and Y attempt to move two identical heavy boxes, P and Q. Man X tries to push box P across the floor. It stays still because something is blocking it. Man Y raises box Q from the floor up onto a shelf. Which man does the greatest amount of work on the box, and which box receives the greatest amount of energy?

May/June 2016

A skier goes from the foot of a ski slope up to the summit and gains $10000\ \text{J}$ of gravitational potential energy. She then skis back down the slope. When she reaches the bottom, her kinetic energy is $2000\ \text{J}$. How much energy is dissipated in overcoming friction and air resistance as the skier moves down the slope?

May/June 2016

Which energy source is renewable and can be depended on to be available at all times?

May/June 2016

Two workers are placing cans onto a shelf in a shop. Each worker lifts the same number of identical cans onto that same shelf from the same starting height. Worker P takes $3.0$ minutes to lift the cans. Worker Q takes $4.0$ minutes to lift the cans. Which statement about the workers is correct?

May/June 2016

A skier travels from the foot of a ski slope to the top, increasing her gravitational potential energy by $10000\ \text{J}$. She then skis back down the slope. When she reaches the bottom, her kinetic energy is $2000\ \text{J}$. What amount of energy is dissipated in work done against friction and air resistance as the skier descends the slope?

May/June 2016

A lorry with a mass of $4000\,\text{kg}$ is moving at a speed of $4.0\,\text{m s}^{-1}$. A car has a mass of $1000\,\text{kg}$. Its kinetic energy is the same as the kinetic energy of the lorry. What is the speed of the car?

May/June 2016

A force is applied to an object, making it travel a certain distance along the direction of the force. Which row shows the situation where the force does the greatest amount of work on the object?

May/June 2016

Which energy resource does not obtain its energy from the Sun?

May/June 2016

Some processes are more efficient than others. Which expression represents the efficiency of a process?

May/June 2016

A stone of mass $m$ is kept stationary in water. It is then released and drops vertically through a distance $h$. The stone then attains a speed $v$. Part of the stone’s initial energy is passed to the water. During the fall, resistive forces make the temperature of both the water and the stone rise. Which expression represents the work done against the resistive forces?

May/June 2016

The diagram illustrates the energy transfer in a modern lamp. An electrical power input of $60\,\text{W}$ results in $12\,\text{W}$ of useful light power output and $48\,\text{W}$ of power wasted as heating the surroundings. Which expression represents the efficiency of the lamp?

May/June 2016

Each of three boxes has a weight of $100\,\text{N}$. A man raises all the boxes together from the ground to a shelf $1.5\,\text{m}$ above the ground. He takes $2.0\,\text{s}$ to complete this. What useful power does the man output in lifting the boxes?

May/June 2016

Which energy resource obtains its energy from a source other than the Sun?

May/June 2016

Fig. 4.1 presents a simplified layout of a geothermal power station.

May/June 2016

Fig. 3.1 illustrates a cabin that carries passengers up a hillside. The cabin is fastened to a cable that travels horizontally from A to B, and then climbs the hill from B to C. The diagram shows pulleys, a cable, a cabin, points A, B and C, a vertical height of 50 m, and a drive pulley linked to an electric motor.

May/June 2016

The diagrams depict athletes training while stretching springs. All of the springs have the same stiffness. Which athlete does the greatest amount of work?

May/June 2017

An energy resource is used to produce electrical energy. Which energy resource depends on a transfer of gravitational potential energy to produce this electrical energy?

May/June 2017

The diagrams illustrate four different athletes as they train by performing pull-ups. Which athlete carries out the greatest amount of work?

May/June 2017

A box with mass $m$ moves down a slope of length $l$ and vertical height $d$ while opposing a frictional force $F$. As the box travels down the slope, it loses gravitational potential energy and does work against friction. Which row gives the decrease in gravitational potential energy and the work done against friction?

May/June 2017

The diagram shows the energy transfers in a device. The device has an efficiency of $50\%$. Which equation is correct?

May/June 2017

A student performs a few simple exercises. In which exercise is the greatest amount of work done?

May/June 2017

An object drops through a vertical distance of $5.0\,\text{m}$. Ignore air resistance. When it reaches the ground, the object has $750\,\text{J}$ of kinetic energy. What is the mass of the object?

May/June 2017

The diagrams illustrate athletes training by stretching springs. All of the springs have the same stiffness. Which athlete does the greatest amount of work?

May/June 2017

A solar panel is used to recharge a battery. The electrical power output from the solar panel is $0.80\,\text{W}$. The panel has an efficiency of $20\%$. What is the power input of the sunlight onto the solar panel?

May/June 2017

The diagrams illustrate four different athletes training by performing pull-ups. Which athlete carries out the greatest amount of work?

May/June 2017

The diagrams illustrate four bodies moving in the directions indicated. In each diagram, the only forces acting on the bodies are shown. Which body gains the greatest kinetic energy when it moves a distance of $1.0\,\text{m}$?

May/June 2017

Fig. 4.1 illustrates a hydroelectric power system in the mountains. The labels are reservoir A, reservoir B, reservoir C, pumping station, pipeline, hydroelectric station and city.

May/June 2017

A student owns a laptop computer. The computer runs from a battery.

May/June 2017

The diagram illustrates the energy transferred by a lamp in 1 second. Which form of wasted energy is produced by the lamp?

May/June 2018

Which energy resource cannot be replenished naturally?

May/June 2018

A student performs work by dragging a box across a level floor. She then drags a second box over the same floor. Which row shows that she is now doing twice the amount of work?

May/June 2018

Which energy source counts as renewable?

May/June 2018

A student carries out work by dragging a box across a level floor. She then drags a second box across the same floor. Which row shows that the student is now doing twice the amount of work?

May/June 2018

An electrical heater passes thermal energy to the surroundings. The graph indicates how the quantity of thermal energy transferred changes with time. The heater keeps transferring energy at the same rate. How much thermal energy is transferred by the heater in $5.0$ minutes?

May/June 2018