TOPIC 1 - ENERGY

Which energy store increases as the bungee cords are stretched?

elastic potential energy

Why will not all of the elastic potential energy be transferred to gravitational potential energy?

air resistance (energy used to overcome)

A solar power system is installed in the remote village in addition to the hydroelectric generator. Explain why this improves the reliability of the electricity supply to the village

the solar power output would be greater when it's sunny; so less variation in total power output

Why is a thermometer likely to be misread?

viewing angle affects measurement/ parallax error

How could you compare the thermal conductivity of two metals and why?

measure the time it takes for two metals to decrease by 20 degrees; because the shorter the time, the higher the conductivity; because the rate of energy transfer is higher

The total power output of the girl was greater than the answer to part (a). Suggest two reasons why

girl increases her kinetic energy; so some energy is wasted in her muscles, energy transferred as thermal energy to surroundings

The baby bouncer should not be used with babies that have a mass greater than 12 kg. Suggest one reason why

the spring may become permanently extended; extensino may be too great

Describe the energy transfers as the baby moves from up to down

• baby has gravitational potential energy

• this is transferred to kinetic energy

• and elastic potential energy 

• all the energy is then in the elastic potential energy

Give one factor which would increase the distance the toy aeroplane travels horizontally before hitting the ground

increasing the extension of the spring; more elastic potential energy; increase the angle of release

Which energy store increases when water is heated?

thermal energy

Explain one change that would reduce the amount of carbon dioxide released by each activity

Transport

• don't use petrol/ diesel car; don't burn ptrol/ diesel

• use electric cars instead/ hydrogen-fuelled cars

• use a bicycle

• use public transport/ walk

Generating Electricity

• don't use coal, oil, gas

• use renewable methods; use nuclear power

• don't use electrical appliances when not needed

• to reduce the demand for electricity generate with coal, oil, gas

Explain one reason why the hydroelectric power output varied

the level of water in a river varies/ amount of rainfall varies; so is lower in the summer months

What are non-renewable energy sources?

coal; oil; natural gas; nuclear

What are renewable energy sources?

solar; wind; hydroelectric; geothermal; tidal; wave; biofuels

Suggest why wind energy can't meet the UK's demand?

wind is unrealiable; wind turbines don't turn when wind too strong/ weak; not enough wind turbines

Explain how oiling would affect the efficiency of the wind turbine

• the efficiency would increase; because percentage of energy usefully transferred would increase; less energy wasted because; less work done against friction

Explain why people should be encouraged to use energy efficient electrical devices

• more efficient devices waste less energy/ need a lower energy input

• which would minimise the electricity/ energy demand/ minimise the environmental impact

In an experiment of measuring the mass lost of an ice cube - name a source of random error

variation in initial mass of the ice cube; surface area of the ice cube touching metal

It is unlikely that all of the electricity that the UK needs can be generated by solar power systems - why?

a really large area of land would need to be covered with solar cells; due to the low useful power output of solar cells (number of hours of daylight is too low)

Why can the toy car and racing track be considered ‘a closed system’?

The total energy of the racing track and the car is constant

Suggest advantages of charging car while driving

• recharging is a continuous process; fewer cells needs in the car; more cars can be charged at the same time

When electric cars are not being driven, energy stored in their batteries could be used to meet sudden peaks in electricity demand. Suggest how

when cars are plugged in; the energy from car batteries could be transferred back to the National Grid

At the bottom of the slide, all riders and their sleds have approximately the same speed. Explain why

-decrease in gravitational energy = increase in kinetic energy

• the equation 1/2mv^2 = mgh

• masses cancel on both sides of the equation

• speed only depends on vertical height + gravitational field strength

• variations will be due to air resistance/ friction; different initial speed

Give two environmental advantages of using a gas-fired power station to generate electricity compared with using a coal-fired power station

• no sulfur dioxide released

• doesn't cause acid rain

• no particulates released

• doesn't cause global dimming

• less carbon dioxide released

• less global warming

What is the frequency of the mains electricity supply in the UK? 50Hz

Why do both switches need to be closed?

to complete the series circuit so charge can flow

When the kettle was switched on the temperature of the water did not immediately start to increase. Suggest why

the heating element of the kettle takes time to heat up

As the person moves down the zip wire her increase in kinetic energy is less than her decrease in gravitational potential energy - why?

work is done against air resistance; causing thermal energy to be transferred to the surroundings

Different people have different speeds at the end of the zip wire. Explain why

different people have different surface areas; so would be affected by air resistance differently OR inital speed may no be zero; which would add to the tota energy of the system

How does cycling uphill affect the maximum speed of this cyclist? Explain your answer

the max speed is lower; because the max power output of the cyclist is constant; bbut additional work is done against gravity/ gravitational potential energy is increased

Why would it be dangerous for the live wire of the electric cable to touch the metal case?

there is a risk of electric shock if someone touched the case

Describe the advantages of nuclear power compared with the use of shale gas to generate electricity

• no CO2 is emitted
• doesn't cause global warming
• doesn't cause earthquakes
• more energy released per kg of fuel

What is the name of one fuel used in nuclear power stations?

uranium; plutonium

What does more energy efficient mean?

a higher proportion/ percentage of the total power input is usefull transfered OR higher power output for the same total power/ energy input

What is a renewable energy resource?

an energy resource that can be replenished quickly

Describe a method the student could have used to obtain the results for the temperature of a kettle against the time

• meausre mass of water with balance; volume with measuring cyclinder
• measure initial temperature of water
• pour water into the kettle
• put temperature probe/ thermometer in water
• switch the kettle on
• record temperature 
• measure time with a stopclock with interval of 5 seconds

Designers of electric car batteries want to increase the amount of energy that can be stored in a battery. Suggest two reasons why

increase the range of electric cars; increase the time between recharged; decrease the total mass of electric car; greater acceleration

What is the risk caused by the hazard of hot water?

scald/ burn to skin

In addition to power input, light bulbs should also be labelled with the rate at which they emit visible light. Suggest why

bulbs also transfer thermal energy; the efficiency of the light blub needs to be considered too

The highest muscle power reading was recorded instead of calculating an average. Suggest one reason why

• max power was being investigated not the mean
• volunteer may not use max effort on the first try
• performance may improve with practice; or get worse with tiredness

Describe a method the student could have used to obtain the results for the temperature decrease of water

• Wrap N layers of newspapers around metal can
• heat water in kettle
• put water in the can
• use a measuring cylnider to measure the volume
• use a stopwatch to measure 5 minutes
• calculate the temperature decrease
• repeat with a no. diff layer of insulation; use same inital temperature of hot water; use same volume of water each time

Suggest why the UK doesn't want nuclear power to be the sole energy provider

• conserves fuel reserves
• spared provide spare capacity in case of power station emergency shut down
• not to make unnecessary environmental impact
• compensate for unreliable renewable resources

The student’s results can only be used as an estimate of the mean power at her location (with pan in the sun)

• angle of solar raditaion changed during ivestigation
• intensity may have varied
• energy used to heat the pan as well as the water; transferred to the surroundings