Physics Paper 1- Major Focus Of Exam Flashcards
What is kinetic energy?
Energy stored in moving objects
Do stationary objects have kinetic energy?
No
What’s the equation to calculate kinetic energy?
1/2 mass x velocity squared
What are the energy changes taking place in a car travelling at constant speed?
Chemical energy in petrol- kinetic energy store
What type of energy is a stretched spring storing?
Elastic potential energy
What is the force directly proportional to?
The extension of a spring
When the graph of force vs extension, when the graph no longer has a constant gradient, what do we call it!
The limit of proptionalott
What’s the equation for elastic potential energy?
1/2 x spring constant x extension
What’s the unit for spring constant?
N/m
What’s the unit for extension?
Metres
What is gravitational potential energy?
Energy stores in an object due to its position above the earths surface
What are the energy transfers when I lift a tennis ball from the ground to a shelf?
Chemical store in my muscles- GPE store of the ball
What’s the equation for GPE?
Mass x g x height
What’s the unit for gravitational field strength?
N/kg
What’s the unit for mass?
Kg
What is the specific heat capacity of a substance?
Energy needed to raise the temperature of 1kg of the substance by 1 degree
What’s the equation for specific what capacity?
Energy/mass x change in temp
What’s the unit for specific heat capacity?
J/kgoC
What is thermal energy?
Energy stored due to an objects temperature
What is the law of conservation of energy?
Energy can be transferred usefully, stored or dissipated but cannot be created or destroyed
In a closed system, can energy enter or leave?
No
On a pendulum, when the mass swings from a fixed point, what are the energy transfers?
GPE- KE-GPE
Why is there maximum kinetic energy at the bottom of the pendulum?
Because that’s when it is travelling the fastest
What’s a problem with energy transfer in a pendulum ?
Haven’t considered friction
What does friction cause?
Energy to be transferred to thermal energy
How can we reduce unwanted energy transfer?
By reducing friction
On a pendulum, how can friction be reduced?
Use a lubricant on the fixed point
Remove air particles around
What’s the energy transfers in a bungee jumper?
GPE- KE-Elastic-KE-GPE
When is the kinetic energy store of a bungee jumper 0
When the rope is fully extended
When is the KE of a bungee jumper at its maximum?
When rope starts to tighten
Why does a bungee jumper never return back to their original position?
Energy is dissipated as thermal energy
Why is energy dissipated as thermal energy for a bungee jumper?
Friction with air particles
Stretching effects on the rope which isn’t fully elastic
When is work done?
When energy is transferred from one store to another
What does mechanical work involve?
Using a force to move
An object
What does electrical work involve ?
A current transferring energy
What’s the equation for work done?
Force x distance
What’s the unit of force?
N
How does a car slow down(energy stores)
Kinetic energy store of car is transferring to thermal store in the brakes as the brakes press against the wheel- temperature of brakes increses
What’s the equation for power?
Energy transferred or work done/time
What’s the equation for efficiency?
Useful output energy transfer/ total input energy transfer
What using the equation for efficiency, what can energy be replaced with ?
Power
What are the 2 ways we can leave our answer for efficiency?
As a decimal or as a percentage %
How can we increase efficiency for a kettle?
Use a pan with a wider base
Use a lid
What’s an issue of using a pan to heat water?
Energy is often used to heat the base of the pan itself
How can be counter the issue of heating water in a pan?
Place the heating element in the water
What type of walls do kettles often have to make them for efficient?
Plastic walls
Finish the sentence, the higher the thermal conductivity of a material, the___
Higher the rate of energy transfer by conduction
What can we pack the wall cavity with to reduce energy transfer?
With an insulating material which has a low thermal conductivity
Besides the walls, where else can thermal energy escape from?
The windows
Why do most houses now have double glazed windows?
They have a low thermal conductivity
What are 2 ways we can reduce thermal energy transfer from a house?
Construct buildings using low thermal conductivity materials
Built houses with thick walls
Describe the practical
Of investigating the effectiveness of different thermal insulators
Place small beaker inside a large beaker
Use kettle to boil water
Transfer 80cm3 of water into small beaker
Use cardboard as a lid for large beaker
Place thermometer through hole in lid
Record starting temp of water and start stopwatch
Record temp of water every 3 mins for
15 mins
Repeat but use a range of insulating materials
What are 3 control variables for the thermal insulating experiment?
Same volume of hot water
Same mass of insulating material
Same starting temperature of water
What’s the independent variable in the thermal
Insulating practical
The insulating material
What’s the dependent variable in the thermal insulating practical?
Temperature
How can we show our results for the thermal insulating practical?
Make a table
Plot a cooling graph
What else can we investigate besides the effectiveness of different toes of insulating material?
How thickness of the material affects insulation
What’s the independent variable when measuring how thickness of
Material affects cooling?
Thickness /layers of material
What’s the equation for power?
Power=pd x current
What’s another equation for power involving current and resistance?
Poee= current squared x resistance
What’s the equation for charge?
Current x tkme
What’s an equation for energy transferred?
Charge x pd
Describe the energy transfers in a blender and a fan
Electrical energy- kinetic energy of
Motors
Describe the energy transfer taking place in an iron and a kettle
Electrical energy- thermal energy
Describe the energy transfers taking place in a hair dryer and a washing machine
Electrical
Energy- kinetic energy of motors+ thermal energy
Do appliance designed to generate thermal energy, usually have a lower or high power rating than others?
Higher
What is power?
Rate at which energy is transferred
What’s the equation for energy?
Power x time
What’s the unit for time?
Seconds
What does the national
Grid consist of?
A system of transformers and high voltage cables
What’s the pathways of electricity from power stations to
Homes ?
Step up transformer- high voltage cables- step down transformer
What’s a problem with getting electricity to homes via wires?
Energy is always lost due to the resistance of the wires
How can we reduce energy loss in high voltage cables in the national grid and thus make it more efficient?
Build Power stations near to
Homes
Use transformers
What does step up transformers do?
Increase the potential difference
Why do we use high pd in cables?
Less energy is lost
What do step down transformers do?
Reduce the potential difference to
Around 230V
Why do we use step down transformers?
Reduce pd before electricity passes to homes- safer
In a solids, how are particles arranged/can they move?
Particles are close together in a regular pattern
They can’t move, they only vibrate
Can particles in a liquid move around each other?
Yes
In a gas, are particles
Moving slow or very fast?
Very fast
What’s the density of a material?
Mass for a given volume
What’s the equation for density?
Mass/volume
Do solids have a high or low density?
High
Why are solids very dense?
Because particles are packed closely together
Do liquids tend to have a low or high density?
High density
Does polystyrene have a low or high density?
Low density
Why does polystyrene have a low density?
Very open structure and is full of air spaces
How can we measure the density of a regular object?
Measure dimensions using a ruler to calculate volume
Determine mass using a balance
M/v
How can we measure the volume of an irregular object?
Fill eureka can with water
Place object into water
Measure volume of water displaced from the spout using a measuring cylinder
=volume of object
What types of energy can particles have
Kinetic and potential
What is potential energy?
Energy stored in intermolecular forces and chemical bonds
What’s the equation for internal energy?
Kinetic+ potential energy
If we heat a solid/liquid, do we increase or decrease the internal energy?
Increase
Does cooling reduce internal energy?
Yes
What is internal energy?
Total kinetic energy and potential energy of all the particles
When changes of state take place, what happens to the mass?
It stays the same- mass is conserved
Are changes of state physical or chemical changes?
Physical
What does it mean when we define changes of state as physical changes?
If we reverse the change, the material recovers it’s original properties
What is evaporation?
When a liquid changes to a gas on the SURFACE of a liquid
When the line plateaus on a heat/cooling graph, what does this mean?
The substance is changing state, temperature isn’t changing
How can a substance change from a solid to liquid when temperature increases?
Energy weakens/breaks the forces of attraction
What is latent heat?
Energy needed for a substance to change state
During a change of state, what are we increasing and keeping the same?
Increasing internal energy
Controlling temperature
Does a cooling graph have a positive or negative gradient?
Negative
What are the changes of state in a hearing graph?
Melting and boiling
What are the changes of state in a cooling graph?
Condensation and freezing
What’s the detailed definition of specific latent heat?
Amount of energy required to change the state of 1kg of the substance with no change in temperature
What change of state does specific latent heat of fusion refer to?
Solid to liquid
What change of state does the specific latent heat of vaporisation refer to?
Liquid to vapour(gas)
What’s the equation for specific latent heat?
Energy/mass
Complete the equation, energy lost from the GPE store=
Energy gained in the kinetic energy store
What causes a car to slow down?
Friction between a cars brakes and its wheels doing work
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
Describe the practical to investigate the effectiveness of different insulators
- Boil water in kettle and transfer to sealable container
- Use thermometer to measure the initial temperature of water
- Seal container and leave for 5 mins- measure time using a stopwatch
- Remove lid and measure final temperature of water
- Pour away water and allow container to cool to room temperature
- Repeat experiment but with container in a different material
What’s a control variables of the thermal insulator practical?
Same mass of water
Initial temperature of water
Container
Describe energy transfers that occur when a car collided with a stationary object
Normal contact force between car and object does work, causing energy to be transferred from cars kinetic energy store to other energy stores
Why doesn’t the equation for elastic potential energy work for all values for extension of springs?
Equation only works if spring hasn’t exceeded limit of proportionality
Why isn’t wave power considered reliable?
Depends on water waves which vary due to winds
Why are fossil fuels reliable?
Enough of them to meet current demand
Why at a bottom of a slide do all riders and their sleds have approximately the same speed?
Energy gained in kinetic store= energy lost in gravitation store, so Ek=GPE
Mass cancels out in both equations
Speeds only depends on height
Only varies due to air resistance
As a person moves down a zip wire her increase in kinetic energy is less than her decrease in GPE, why?
Work is done against air resistance
Causes thermal energy to be transferrred to surroundings
Why do different people have different speeds at the end of the zip wire?
People have different masses
Affected by air resistance differently
People have different terminal velocity
Give 2 advantages of using data loggers and temperature probes compared to a thermometer
Higher resolution
Takes readings automatically
Explain how evaporation of a liquid causes teneprature if remaining liquid to decrease
Particles with most energy leave surface of liquid
Reduced average kinetic energy of remaining particles
Advantage of radioactive waste having a shorter half life
Activity decreases quickly
Risk of harm decreases quickly
Explain what type of error would be caused if the students eye was not in the line with the level of the liquid in the tube
Random error
Eye position not same each time
Why does the internal energy of the air increase as the tyre is inflated
Work is done on the air
Temperature of air increases
Explain how a zero error can be corrected
Record value of zero error with no object
Subtract value of zero error
Describe a method to investigate temp decrease with diff layers of newspaper
Heat water with kettle Measure vol of water using measuring cylinder Transfer to metal can Measure initial temp Use stopwatch to time 5 mins Measure final temp Calculate temp difference Repeat with diff layers of newspaper Control variables= Initial temperature and vol of water
Describe how energy is generated in a hydroelectric power station
Water moves form high to low
GPE goes to KE
Water rotates turbine to turn a generator
Transfer KE to electrical energy
Describe how to measure the volume of an irregular object
Fill eureka can with water
Water level with spout
Place object in water
Collect displaced water and measure the volume using a measuring cylinder
What’s a potential improvement for the insulator practical?
Use a cardboard lid and cut a hole for the thermometer
Does current increase or fevered when resistance decreases
Decreases
Explain why the resistance of a filament bulb changes as the current through it is increased
As current increases, filament gets hotter.
Because temeprature rises, resistance increases
Why is a radioactive isotope that emits alpha radiation not suitable for use as a tracer?
Lowly penetrating so can’t pass in or out of the human body
Why does a half life of 6 hours suitable for use as a tracer?
Allows sufficient time to conduct investigation whilst not being in the patients body for long
Explain why a patient that ‘emits’ beta and gamma radiation should be isolated
Patient s body is contaminated
Beta and gamma are highly penetrating so can pass into other people and there’s a risk of harm
Describe what must happen for a chain reaction to become established in a sample of uranium
Free neutrons shoddiness by uranium nucleus
Undergoes fission
Releases neutrons
Why is the specific heat capacity larger in a substance in solid state than liquid
Because temperature rise is smaller in a solid
Why do you wear polythene gloves when handling radioactive materials?
Prevent contamination and this any potential long lasting damage
Explain is energy release by the chain reaction is affected by moving the control rods
Lowering the control rods increases neutrons absorbed, lowering the energy released
Why would an electrician receive an electric shock if he touches the live wire
Pd of live wire is 230V and his pd is 0V
So large pd difference, so current passes through his body
Why it this is a good model for the random nature of radioactive decay
Can’t predict which dice will decay
Can’t predict when
Why would a student less likely receive an electric chock if he walks on thin copper wires in a carpet
Copper has low resistance, so a lower build up of charge
How does cycling uphill affect the maximum speed of a cyclist
Maximum speed is lower
Because maximum power output is constant
But gravitational potential energy is increded
What does energy efficient mean?
Higher period energy input is usefully transferred
Why does a smoke work sketch on when smoke particles enter the plastic casing?
Smoke
Absorbs alpha radiation
Why would a smoke alarm not work with a radiation source that emits beta or gamma?
It will penetrate smoke, so no change is detected
Explain the ideal properties of a radioactive source for use in medical diagnosis
Low ionising
Short half life
Highly penetrating-easily pass through body
Emits gamma
Describe the effect on lower output when wind speed is halved
Mass decreases by a halve
Wind speed also decreases by a halve, so kinetic energy is deceresed by factor of 4
So kinetic energy deceresed by factor of 8
