Topic P1 - Energy Flashcards
(110 cards)
1
Q
What is Energy?
A
It is the ability for an object to do work.
2
Q
When work is done by an object energy is transferred?
A
From the object e.g. when a balloon pops the air inside it does work to surrounding air.
3
Q
When work is done on an object energy is transferred?
A
To the object e.g. When a man pushes a box, he is transferring energy to the Box.
4
Q
What is Energy measured in?
A
Joules (j)
5
Q
1 ( kilojoule ) equals how many joules?
A
1000J
6
Q
Convert 9 KJ to joules?
A
9000 joules (j)
7
Q
9 J equals how many kilojoules
A
0.009 KJ
8
Q
1 Megajoule equals how many Joules?
A
1,000,000 J
9
Q
What is the Pneumonic to learn the 8 stores of energy?
A
Geeks Lunch(heat = thermal and U doesn’t stand for anything.
10
Q
What are the 8 stores of energy?
A
1) Kinetic energy
2) Thermal
3) Gravitational potential energy
4) Elastic potential
5) Chemical
6) Magnetic
7) Electrostatic
8) Nuclear
11
Q
What is Thermal energy also known as?
A
Internal energy.
12
Q
What are the 4 pathways energy can be transferred from?
A
1) Mechanical ( forces doing work)
2) Electrical ( using electrical currents)
3) Heating ( temperature difference)
4) Radiation ( light or Electromagnetic)
13
Q
What is a System?
A
A system is an object or a group of objects.
14
Q
Identify the systems, and energy changes in a catapault ready to fire a ball?
A
Our system is the catapault and the ball, the energy starts in the elastic store within the catapault. When it is fired the energy is transferred along the Mechanical pathway, most of it will go the kinetic store of the ball, some will go into thermal store of catapault ( the elastic will warm up)
15
Q
What is the Conservation of energy?
A
Energy cannot be created or destroyed, only transferred between a system.
16
Q
What are closed systems?
A
Are systems where neither matter nor energy can enter or leave.
17
Q
If a ball is thrown into the air with O Joules of Gravitational potential energy and 10 Joules of kinetic what is the amount of GPE and kinetic when the ball is stationary?
A
When it is about to start falling the ball has 10 J of GPE and 0 joules to the kinetic energy.
18
Q
Describe the energy transfers when a ball is thrown vertically upwards?
A
Energy is transferred from the kinetic energy store to its gravitational potential energy store.
19
Q
Describe the energy transfers when kicking a football?
A
Energy is transferred from the chemical store in our bodies to the kinetic energy of our foot, which in turn is transferred directly to the Kinetic energy of the ball.
20
Q
Describe the energy transfers of a wind- up toy?
A
Energy is transferred from the Elastic potential store of the spring inside to its Kinetic energy store.
21
Q
Describe the energy transfers when we heat water inside a kettle?
A
Energy is transferred electrically to the thermal store of the water.
22
Q
Describe the energy transfers when a driver breaks and decelerates the car to rest?
A
Its kinetic energy is transferred to the thermal energy store in the brakes and temperature of brakes increase.
23
Q
Describe the energy transfers when two like poles repel of magnets?
A
Energy will be transferred to the magnetic energy store to the kinetic energy store of both magnets.
24
Q
Describe the energy transfers when we burn wood in a fire?
A
Energy is transferred from the chemical store of the wood to the thermal store of the surrounding air.
25
Describe the energy transfers when we power a filament bulb using a battery?
Energy will be transferred from chemical energy store of battery, to thermal store of filament.
26
A car with an energy input of 500,000J from chemical potential energy transfers 350,000J into kinetic energy and 25,000J into light energy. Explain how you would calculate the energy it transfers into the thermal energy store.
The law of conservation of energy states that the total energy at the start and end of the process is the same.
This means that the total energy output must be 500,000J, becuase the total energy input is 500,000J. This means thermal energy is 500,000 - 350,000 - 25,000 = 125,000J
27
Explain why lifting an object up 10m on Jupiter stores more gravitational potential energy than lifting the same object up 10m on Earth
this is becuase Jupiter has a stronger gravitational field strenght than Earth. This means it has a stronger acceleration due to gravity (g).
As gravitational potential energy = m x g x h. If g is larger then gravitational potential energy is also larger.
28
What are the energy transfers for a torch
Chemical potential energy --> Electric potential energy --> Light energy
29
What are the energy transfers for a falling ball?
Gravitational potential energy --> Kinetic energy --> Sound and thermal energy
30
Why is it possible that humans might 'run out' of energy even though it cannot be created or destroyed
When we transfer energy, some of it is dissipated into thermal energy in the environment, where we cannot access it. The energy is still present but we are unable to make use of it, so we could run out of the energy that we are able to use.
31
If an object is more higher up what does this mean?
Higher GPE
32
Describe the energy transfers that occur when the wind causes a windmill to spin?
Energy is transferred mechanically from the kinetic energy store of the wind to the kinetic energy store of the windmill.
33
Explain why your hands get hotter when you rub them together
When you rub your hands together the force of friction acts over a distance. This causes the transfer of energy from chemical store to the thermal store, this makes your hands heat up.
34
Explain why a roller coaster cannot roll up the track to the same height as the peak that it has just come from
This is due to energy dissipation as thermal energy into the environment. When the roller coaster rolls down the track some of the energy is dissipated out of the system as thermal energy. This means that the total energy in the system has reduced, reducing the maximum gravitational potential energy it can gain
35
What is the Equation for Kinetic energy and units?
KE = 1/2 x m x v2
Mass is measured in kilograms (kg)
velocity is measured in meters per second (m/s)
Kinetic energy is measured in joules (J)
36
A car of mass 1500 kg is travelling a speed at 20 m/s . Calculate its Kinetic energy?
KE = 1/2 x m x v2
= 1/2 X 1500 X 20 sqaured
= 15000 J
37
What is Limit of Proportionality?
The spring has been stretched so much that it cannot return to its original length.
38
What is the Equation of Elastic potential energy and what are the units?
elastic potential energy = 1/2 x spring constant x extension squared
EPE = 1/2 x k x e2
Elastic potential energy is measured in joules (J)
Spring constant is measured in Newtons per meter (N/m)
Extension is measured in meters (m)
39
A steel spring constant 5 N/M is initially 10 cm long. Calculate the increase in the Elastic potential energy when it is increased by 15 cm ?
EPE = 1/2 x k x e2
e = 5 cm = 0.05 m
1/2 X 5 X 0.05 squared = 0.00625J
40
What is the Equation of Gravational potential energy and what are the units?
Gravitational potential energy = mass x gravitational field strength x height
GPE = m x g x h
Gravitaitonal potential energy is measured in Joules (J)
Mass is measured in kilograms (kg)
Gravitational field strength is measured in meters per second squared (9.8 N/Kg)
Height is measured in meters(m)
41
A book of a mass of 400 g is lifted from the floor onto a 1.2 m high shelf. Calculate the increase in GPE of the book. Take G = 9.8 N/Kg?
m = 0.4 kg
| 0.4 kg x 1.2 X 9.8 = 4.7 J
42
When a Object falls its Gravitational potential energy stored is transferred where?
To its kinetic energy store
43
What is Air resistance?
It is the friction between the air and an object
44
For a falling object when there is no air resistance energy lost from Gravitational potential energy is store equals what?
Energy gained in the kinetic energy store.
45
A lorry of a mass of 5000 kg is parked on a 20 m long 1 in 10 slope ( a one in ten slope goes down 1 m every 10 m traveled along the slope) when its handbrake is released, it rolls down the slope.
a) Calculate its decrease in Gravitational potential energy by the time it is reached down the slope
B) Calculate the speed at the bottom of the slope?
1) Ep = M X G X H
5000 kg X 9.8 X 2 = 98000J
```
2) Energy lost in GPE = Gain in KE
98,000 J = 1/2 X M x V squared
98,000 J = 1/2 X 5000 X V squared
V squared = 39.2
V = 6.26 m/s
```
46
A 2.0 kg object is dropped from a height of 10 m. Calculate the speed of the object after it has fallen 5.0m, assuming there is no air resistance. Give answer in 2 significant figures. (5 marks)
```
Ep = 2 X 5 X 9.8 = 96 J
Loss in GPE = Gain in GPE
Ek = 1/2 m X v squared
96J = 1/2 X 2 X v squared
V squared = 2Ek / 2
= 98 m (squared) / s (squared
```
47
When a spring is released, the decrease in elastic potential energy equals what?
Increase in Kinetic energy of spring.
48
The spring in a pinball machine has a spring constant of 60 N / M. When fully compressed, its length decreases by 10 cm. Calculate the Maximum speed at which the pinball of mass 40 g can be released by a spring.
```
decrease in elastic potential energy = Increase in Kinetic energy
1/2 Ke squared = 1/2 mv squared
e = 0.1 m and mass = 0.04 kg
1/2 X 60 X 0.1 squared = 1/2 X 0.04 X V squared
= 0.6 = 0.04 v squared
v squared = 0.6/0.04
v squared = 15
v = 3.87 m/s
```
49
A group of friends are doing some archery.
When Brian fully stretches the bow, it stores 10 J of energy. Describe the energy transfer that occurs as Brian stretches the bow.
Chemical potential energy to elastic potential energy
50
What is the Specific heat capacity?
The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1 kg of the substance by 1'C.
51
What is the equation for the specific heat capacity and what are the units?
E = m × c × θ
E is the energy transferred in joules, J
m is the mass of the substances in kg
c is the specific heat capacity in J / kg °C
θ (‘theta’) is the temperature change in degrees Celsius, °C
52
How does specific heat capacity relate to the time that it takes for an object to cool down?
The higher the specific heat capacity, the longer it takes for something to cool down. This is because a higher specific heat capacity means that something needs to loose more energy to drop in temperature by each degree.
As it has to loose more energy to cool down it means that it takes longer for it to happen
53
Calculate the energy required to increase the temperature od 2kg of water from 20 ' C to 100 ' C. The specific heat capacity of water is 4200/kg'C
```
E = m × c × θ
E = 2 X 4200 X 80
E = 672, 000 J
```
54
An aluminium saucepan of mass 1.2 kg is at a temperature of 120 'C, when taken of stove, 108 KJ of heat energy is lost from the saucepan, Calculate the final temperature of saucepan. ( the specific heat capacity of aluminium is 900J/Kg'C)
Starts with temp of 120 ' C
We need to find final temperature which is lower
E = m × c × θ
Because we are losing energy E is negative
-108,000 J = 1.2 X 900 X θ
θ = E/ M x C
-108,000 / 1.2 X 900 = -100 ' C therefore the temperature has dropped by 100 'C.
Final temperature = 120 - 100 = 20 'C
55
Find the final temperature of 5 Kg of water, at an initial temperature of 5 ' C after 50 KJ of energy has been transferred to it. The specific heat capacity is 4200 J/kg'C (3 marks)
E = m × c × θ therefore
θ = E / (m X c )
50,000 J / ( 5 X 4200) = 2.4 'C
So the new temperature is 5 + 2.4 = 7.4 'C
56
In an experiment 0.2 kg of lead shot is dropped through a vertical distance of one- metre. Assuming that the GPE lost by the lead is transferred entirely into its own thermal store, calculate the increase in the temperature of the lead when it is dropped through a distance 50 times. The specific heat capacity of lead is 128 J/ kg ' C.
Loss of GPE (1 drop) = mgh = 0.2 X 9.8 X 1 = 1.96 J
Loss of GPE ( 50 drops) = 50 X 1.96 = 98 J
Gain in thermal energy is 98J
E = m × c × θ
θ = E / (m X c )
θ = 9.8/ 0.2 x 128
Increase in temp of 3.8 'C
57
What is the method to find the specific heat capacity of a material?
1) Measure the mass of the block
2) Place thermometer and heater into the block
3) Read starting temperature of block
4) Wrap an insulating layer of newspaper to reduce thermal energy to the surroundings.
Connect a joulmeter connected on to a power pack to the heater. ( the joulmeter tells us how many joules of electrical energy is passed into heater.)
6) Leave for some time to allow the temperature to rise.
7) Read how many joules passed into heater and final temperature of block.
8) Find specific heat capacity using equation.
58
What does the term 'energy dissipation' mean and how does it happen?
Energy dissipation means that energy is transferred into stores where humans cannot make use of it.
The most common form of energy dissipation is when the energy is transferred into thermal energy in the environment. When this occurs the energy becomes 'spread out' and we are unable to access it.
59
How is energy dissipated through moving parts of a machine?
Friction between moving parts of a machine can lead to dissipated energy in the form of heat.
60
What two things limit the maximum speed of a car or vehicle?
Friction and air resistance
61
Name 2 ways we can reduce the amount of energy dissipated from a system which has moving parts?
1) Lubricants reduces the friction between the moving parts of a machine
2) Making vehicles streamlined reduces the amount of air resistance excreted on to them.
62
Describe how energy is dissipated through the a system such as a Mobile phone?
When you use your phone energy is usefully transferred from the chemical energy store of the battery in the phone, but some of the energy is dissipated in this transfer to thermal energy store of the phone ( this is why phones get home).
63
What is power?
Power is the rate at which energy is transferred or the rate at which work is done.
64
What is the equation of power?
P (W) = E/T
| P (W) = W/T
65
1 Kilowatt equals how many watts?
1000W
66
1 MW equals how many watts?
1,000,000 W
67
A battery transfers 3KJ of energy to a filament bulb in 20 minutes. Calculate the power output of the bulb?
```
E= 3000 J
T = 20 X 60 = 1200 S
P = 3000 J / 1200s = 2.5 W or 2.5 J/S
```
68
A crane lifts a 1200 kg load through a distance of 10 cm in 40 seconds. Calculate the amount of GPE which is transferred to the load by the crane. Take g = 9.8 N/kg.
B) Hence, calculate the power of the crane, assuming that it is 100 % efficient
Ep = mgh = 1200 X 9.8 X 20 = 117, 600J
b) P= E/T
117,600/40= 2,940 W
69
A plane of mass 10,000 kg accelerates from 150 m/s to 200 m/s in a time of 10 seconds. Calculate the increase in kinetic energy of the plane in this time.
Hence calculate the power output of the engines of the place, assuming that the conversion of the energy supplied to them to the kinetic energy of the plane is 100% efficient.
Intial Ek = 1/2 m v squared = 1/2 X 10,000 X 150 squared = 112,500,000J
Final Ek = 1/2 X 10, 000 X 200 squared = 200,000,000 Joules
Increase in Ek = Final Ek - Intial Ek = 87, 500,000 Joules.
B) Increase in Ek of the plane = Work done by engines = 87,500, 000 joules.
P=E/t = 87,500,000 J/10 s = 8,750, 000 W
70
What is Conduction?
Solids are tightly packed together, when you heat the solid from one end, the energy is transferred to its kinetic energy store of its particles, causing the particles to vibrate more and collide with each other.
71
What is Convection?
When you heat liquid, this causes the particles to gain heat energy, meaning the particles move further apart, meaning the warm water is less dense, therefore the water rises and cool water sinks to the place.
72
What is Thermal conductivity?
It is a measure of how quickly energy is transferred through a material in this way, materials with a high thermal conductivity transfer energy between their particles at a faster rate.
73
Name 4 ways Buildings are designed to reduce the rate of energy transfer by heating.
1) Double glazed windows
2) Thick walls
3) Cavity walls
4) Loft insulation
74
How are Double glazed windows used to reduce the rate of energy transfer by heating?
Have a low thermal conductivity, so less thermal energy can pass through and leave house.
75
How are Thick walls windows used to reduce the rate of energy transfer by heating?
This reduces the rate of thermal transfer.
76
How are Cavity walls windows used to reduce the rate of energy transfer by heating?
Lots of energy is lost from walls of house, therefore people use cavity walls for insulation. Cavity walls have double walls with a gap in the middle. There is insulating foam in the gaps, it has a low thermal conductivity because it is a poor conductor of thermal energy.
77
How are Loft insulation windows used to reduce the rate of energy transfer by heating?
Have a low thermal conductivity
78
What are the 2 formula's for efficiency?
1) Useful output energy transfer/ total input energy transfer.
2) Useful power input/ total power input.
79
A blender is 70% efficient. It has a total input of 600 W. calculate the useful output power.
70 % = 0.7
| Useful power output = efficiency X total power input.
80
What is Non-renewable energy?
when they have been used up, there will be no more left as they take millions of years to form.
81
Name 3 non-renewable sources of energy.
Fossil fuels which are
1) Coal
2) Oil
3) (Natural)Gas
82
What are the 2 main disadvantages of Non-renewable energy?
1) Release greenhouse gases including Carbon dioxide which contributes to Global warming./sulfur dioxide causing acid rain and breathing problems.
2) They will run out
83
What are the 3 main advantages of Non-renewable energy?
1) Short start up time
2) Relatively cheap
3) Provide most of our energy
84
What are Renewable energy?
Energy resources is one that is being or can be replenished as it is used
85
What are 7 types of Renewable energy?
```
Wind power
Solar power
Hydroelectric power
Tidal power
Bio-fuels
Geothermal
Wave power
```
86
What are advantages to Renewable energy?
1) Never run out
| 2) Doesn't add carbon dioxide to the atmosphere and do not contribute to climate change.
87
What are disadvantages of Renewable energy?
Wind and solar are not reliable ( some days not windy and solar power doesn't work well in cloudy days.
88
What are the 2 main uses of Energy resources?
Transport and heating
89
What are 3 advantages of Wind power?
No pollution
Renewable and clean
Can be reliable ( it decreases the amount of fossil fuels being burnt.
90
What are 3 disadvantages of Wind power?
1) Noisy
2) Can spoil view (they cover a lot of ground)
3) Unreliable if there is no wind so you cannot increase the supply.
91
What are solar cells?
The sunlight that falls on a solar cell is used directly for generating electricity.
92
What are 2 advantages of Solar cells?
1) No pollution
| 2) Very reliable source in sunny countries
93
What are 3 disadvantages of Solar cells?
1) Unreliable in some countries (cannot increase the power output when there is extra demand)
2) Initial costs are high
3) Relatively small scale
94
What is Geothermal power?
these schemes involve the use of water or steam which is heaved naturally by process within the Earth's crust and below for the generating electricity. Usually used in volcanic countries.
95
What are 2 advantages of Geothermal power?
1) Free energy that is reliable
2) do very little to the environment
3) Geothermal power plants can run continuously as they transfer energy from the thermal energy store of the ground.
96
What are 2 disadvantages of Geothermal power?
1) Aren't suitable locations for power plants
| 2) Cost of building a power plant is often high compared to the amount of energy it produces.
97
What is Hydroelectric power?
Usually requires the flooding of a valley by building a big dam, water is allowed through turbines.
98
What are 2 advantages of Hydroelectric power?
1) No pollution
| 2) It can provide an immediate response to an increased demand for electricity
99
What are 2 disadvantages of Hydroelectric power?
1) Big impact on environment due to flooding of the valley ( rotting vegetation and loss of habitat)
2) Only can generate on a small scale
100
What are 2 advantages of Wave power?
1) Doesn't produce Carbon dioxide
| 2) No pollution
101
What are 3 disadvantages of Wave power?
1) Not reliable, the strength of the wave depends have windy it is.
2) Unlikely to produce a wide scale of energy.
3) Noisy which could affect wildlife.
102
What are tidal barrages?
They are big dams built across river estuaries.
103
What are 2 advantages of Tidal barrages?
1) Reliable as tide comes in 2 a day
| 2) Can produce a large amount of electricity in a reliable way
104
What are 2 disadvantages of Tidal barrages?
1) Expensive
| 2) Destructive to wildlife habitats e.g birds
105
What are bio-fuels?
Biofuels are fuels that are produced from living organisms. For example using ethanol created by bacteria or burning plants directly to generate electricity.
106
What are 2 advantages of Bio-fuels
1) Reliable as crops take a short time to grow
2) Carbon neutral (which means that they release only as much carbon dioxide when they burn as was used to make the original oil by photosynthesis.
107
What is the main disadvantage of Bio-fuels
1)The problems that they can cause is that land is used to grow fuel crops instead of food. This can lead to food shortages as farmers switch to growing more profitable fuel crops
108
Describe the environmental impact of using oil as energy resource for generating electricity?
1) Oil spillages can occur when transporting oil, which can kill animals that live in and around the sea.
2) It produces sulfur dioxide causing acid rain which is harmful to animals having an affect on their ecosystems.
109
Give 2 benefits of power plants that use fossil fuels.
1) they're reliable
| 2) They can respond quickly to changes in demand
110
What are 3 reasons why we currently do not use more renewable energy resources in the UK.
1) Renewable energy resources are less reliable than non-renewable energy resources.
2) building new power plants are expensive and people don't want to live next to them
3) hybrid cars are more expensive than the equivalent of petrol cars
