Papper One Physics Flashcards
What are the eight types of energy source
Thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear
What is a closed system
Where neither matter nor energy can enter or leave and the net change in total energy of a closed system is always zero
What does work done mean
Energy being transferred
What is a system
An object or group of objects
If an apple falls from a tree what is happening to transfer of energy
Energy is transferred from gravitational potential energy to kinetic energy store
What is kinetic energy
Energy store in moving objects
What is the kinetic energy of stationery objects
Zero
A car with a mass of 700kg is moving with a speed of 20 m/s. Calculate the kinetic energy for the car
Kinetic energy = 0.5 x mass x speed^2
Kinetic energy = 0.5 x 700 x 20 = 140,000 J
Kinetic energy = 140 KJ
A cyclist and bike have a total mass of 100Kg and a speed of 15 m/s. Calculate the kinetic energy.
Kinetic energy = 0.5 x m x v^2
Kinetic energy = 0.5 x 100 x 15^2=11250 J
Kinetic energy = 11.25 KJ
A tennis ball is travelling at 50 m/s and has a kinetic energy of 75J. Calculate the mass of the tennis ball.
Kinetic energy = 0.5 x mass x speed^2
Mass = kinetic energy / 0.5 x speed^2
75/0.5 x50^2
Mass = 0.06 kg
What happens when you stretch a spring
We’re applying a force to change the length of the spring
When you put energy into a spring to stretch it the stretch spring is storing this energy and we call that…
Elastic potential energy
What is the relationship between extension(m) and force applied(N)
Directly proportional
What is gravitational potential energy
Energy stored in an object due to it’s position above earth’s surface
A crane lifts a 75kg mass a height of 8m. Calculate the gravitational potential energy gained by the mass. (Gravitational field strength = 9.8 N/kg)
Gravitational potential energy = mass x gravational field strength x height
GPE = 75 x 9.8 x 8 = 5880 J
A ball with a mass of 500g is lifted onto a shelf which is 1.5m above the ground. Calculate the gravitational field strength gained by the ball.
GPE = mass x height x GFS
GPE = 0.5 x 9.8 x 1.5
GPE = 7.35 J
Calculate the energy required to increase the temperature of 2kg of water from 20oc to 100oc. The specific heat capacity for water is 4200 j/kg 0c
Change in thermal energy = mass x specific heat capacity x temperature change
Change in thermal energy = 2 x 4200 x 80 = 67200
=672 kj
An iron has aluminium plate with a mass of 1.5kg. Calculate the thermal energy stored in the plate when the temperature rises from 20oc to 200oc. The specific heat capacity of aluminium is 913 J/kgoc
Change in thermal energy = mass x specific heat capacity x temperature change
Change in thermal energy = 1.5 x 913 x 180 =246510J
Kinetic energy definition
The energy stored in a moving object
Gravitational potential energy definition
The energy stored due to an objects position above the ground.
Elastic potential energy definition
Energy stored in a stretched spring
Thermal energy definition
Energy stored due to an objects temperature
What is the law of conservation of energy
Energy can be transferred usefully, stored or dissipated but it cannot be created or destroyed
How can u reduce unwanted energy transfers
We can reduce unwanted energy transfers by reducing friction.
-use a lubricant e.g. oil on the fixed point
-remove air particles from around the pendulum
When energy is transferred from one store to another…
Work is done
What does mechanical work involve
Using a force to move an object
What does electrical work involve
Current transferring energy
Energy is transferred between stores via ‘pathways’ , the four examples are:
Work done by a force(mechanical)
Work done by an electrical current(electrical)
Radiation
Heating
During braking, a force of 2000 N is applied to the brakes of a car. The car takes 20m to come to a stop. Calculate the work done
Work done(J) = force(N) x distance(m)
Work done = 2000 x 20 =40,000 J
Power definition
The rate at which energy is transferred or the rate at which work is done
When a car stops, 40,000 J of work is done by the brakes in a time of 5 seconds. Calculate the power of the brakes
Power = work done(J)/time(s)
Power = 40,000/5=8000W
A motor transfers 500 J of electrical energy into gravitational potential energy in 40s. What is its power?
Power = energy transferred/time = 500/40
Power = 12.5 W
An electrical current delivers a power of 60 watts to a light bulb. 3 watts of electrical energy are transferred to light energy. Calculate the efficiency of the bulb.
Efficiency = useful power output/total power input
Efficiency = 3/60 = 0.05 x 100 = 5%
Describe ways to increase the efficiency of an energy transfer
Reducing wasted energy
Describe thermal conductivity
The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across that material
How can you reduce the thermal energy transfer from a house
Construct the building using materials with a low thermal conductivity. Build the house with thick walls as this also reduces the rate of thermal energy transfer
What is specific heat capacity
The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1kg of the substance by 1oc
Required practical- specific heat capacity
- Place a beaker on a balance and press zero
- Now add the oil to the beaker and record the mass of the oil
3.place a thermometer and an immersion heater into the oil - Wrap the beaker in insulating foam to reduce thermal energy transfer to surroundings
5.connect a joulemeter to the immersion heater - Time for thirty minutes
- Read number of joules of energy that passed into the immersion heater
8.record the final temperature of the oil
0.95kg of oil was heated from 20oc to 75oc. 87258 J of electrical energy passed into the immersion heater. Calculate the specific heat capacity of the oil.
Specific heat capacity = change in thermal energy/mass x temperature change
Specific heat capacity = 87258/0.95 x 55 = 1670
Sources of inaccuracy examples in the specific heat capacity practical
Thermal energy passing out of the beaker into the air
Not all thermal energy passing into the oil
Incorrect reading of thermometer
Thermal energy not being spread through the oil
What are three uses of energy
Transport
Generating electricity
Heating
Fossil fuel examples
Coal
Oil
Gas
Fossil fuel advantages
They are reliable and always provide energy when we need it.
They also release a great deal of energy. They are abundant and relatively cheap.
They are extremely versatile
Fossil fuel disadvantage
Burning fossil fuels releases a huge amount of carbon dioxide
Fossil fuels are non renewable. They are not being replenished as we use them
Burning fossil fuels can release other pollutants.
E.g. diesel-carbon dioxide particles and nitrogen oxides
E.g. coal-sulfur dioxide leads to acid rain
What is nuclear power
Nuclear power is non reliable. Nuclear power plants run on the elements uranium and plutonium.
Nuclear power advantages
Once a nuclear power plant is running It does not release any carbon dioxide, therefore nuclear power does not contribute to climate change.
Nuclear power is extremely reliable, it generates a lot of electricity exactly when we want it
Nuclear power disadvantages
Nuclear power plants contain highly dangerous radioactive materials. If there’s an accident then these materials could be released into the environment.
Decommissioning a nuclear power plant takes many years and is extremely expensive
Nuclear power plants generates large amounts of highly dangerous radioactive waste. This must be stored for thousands of years before its safe
What is coal used for in the 1900s
All heating and cooking in UK
Electricity came from burning coal
Why did UK switch from coal to gas
Burning gas generates less carbon dioxide than burning coal. This contributes less to climate change.
Gas fired power stations are flexible. They can be switched on quickly during periods of high demand(short start up time). Coal-fired power stations have a very long start-up time
Why did the UK switch from gas to renewables
In the 1970s, scientists began to realise that carbon dioxide emissions from human activity could be leading to climate change. At the politicians did not really see that as a big issue .
Energy from fossil fuels was very cheap. This is an economic factor. Switching away from fossil fuels costs money and that would cost jobs
Renewable energy sources e.g.
Wind power
Solar power
Hydroelectric power
Geothermal
Wave power
Biofuels
Tidal power
Advantages of renewable energy resources
Renewable energy resources will never run out
Once in place, renewable energy resources do not add any carbon dioxide to the atmosphere. They do not contribute to climate change
Describe hydroelectric power
Hydroelectricity is only really useful in countries which have lots of rivers so it’s not really suitable for the UK
Describe tidal power
Extremely reliable. At the moment, the UK does not generate any electricity from tidal power
Describe wave power
Reliable and has huge potential in the UK which has an extensive coastline
Drawback of tidal power
Some people believe its harmful to wild life
Describe geothermal
Geothermal energy uses heat from the earth to generate electricity and heat buildings
Petrol car compared to electric car
A lot of energy used in the UK is for transport, including cars. Almost all cars in the UK run on petrol or diesel which are fossil fuels.
Describe biofuels
Biofuels are produced from plant materials. Burning biofuels does not add extra carbon dioxide to the atmosphere(carbon neutral)
What is current
Flow of electric charge around a circuit
What is the unit of electrical current
Ampere(A)
How can we measure the current in a circuit
Ammeter
How does Step up transformer efficient
Step up potential difference which means the current is lower and less energy is wasted as heat
What does 1 volt of potential difference tell us
1 joule off energy is transferred for each coulomb of charge that is moving through the circuit
