Paper 1 Flashcards
What are the different energy stores?
- KINETIC
- THERMAL (internal energy)
- ELASTIC POTENTIAL
- GRAVITATIONAL POTENTIAL
- MAGNETIC
- NUCLEAR
These stores represent different forms of energy that can be found in an object.
What is KINETIC energy?
Energy of an object in motion.
Kinetic energy is associated with the movement of an object.
What is THERMAL energy also known as?
Internal energy.
Thermal energy refers to the energy contained within an object due to the kinetic energy of its molecules.
What is ELASTIC POTENTIAL energy?
Energy stored in an object when it is stretched or compressed.
This energy is related to the position of an object, like a compressed spring.
What is GRAVITATIONAL POTENTIAL energy?
Energy stored due to an object’s position in a gravitational field.
This energy depends on the height and mass of the object.
What is MAGNETIC energy?
Energy stored in magnetic fields, such as between two magnets.
This energy is associated with magnetic forces acting on objects.
What is NUCLEAR energy?
Energy released from the nucleus of an atom during nuclear reactions.
Nuclear energy can be released in processes like fission or fusion.
Name the four ways energy can be transferred between stores.
- MECHANICALLY
- ELECTRICALLY
- BY HEATING
- BY RADIATION
Understanding these methods is crucial for analyzing energy transfers in physical systems.
What happens during MECHANICAL energy transfer?
A force does work on an object.
This is illustrated by a force pushing an object along a surface.
What is an example of ELECTRICAL energy transfer?
Current flowing through a light bulb.
This demonstrates how electrical energy is converted to light and heat.
What occurs during energy transfer BY HEATING?
Energy is transferred from a hotter object to a colder object.
An example is heating water in a pan on a stove.
What is energy transfer BY RADIATION?
Energy transferred through waves, such as sound or light.
A common example is sunlight traveling to Earth.
Define a closed system.
A system where no matter or energy can enter or leave.
In a closed system, energy is conserved, meaning total energy remains constant.
What happens when a closed system changes?
There is no net change in the total energy of the system.
This is exemplified by energy transfer within a sealed environment.
Fill in the blank: A cold spoon sealed in a flask of hot soup is an example of a _______.
closed system.
This example illustrates energy transfer without loss to the surroundings.
What does the Conservation of Energy Principle state?
Energy is moved between stores and never disappears.
Is energy ever lost during transfers?
No, energy is never lost; it is transferred to a different store.
What happens to energy when it is dissipated?
It is transferred to an energy store that we didn’t want.
What is the relationship between work done and energy transferred?
Work done is the same as energy transferred.
When is energy transferred mechanically?
When a force moves an object.
Describe the energy transfer when a ball is thrown into the air.
Energy is transferred from the boy’s chemical energy store to the ball’s kinetic energy store.
What happens when a ball is dropped from a height?
Energy is transferred from the ball’s gravitational potential energy store to its kinetic energy store.
How does friction affect a car slowing down?
Energy is transferred from the wheels’ kinetic energy store to the thermal energy store of the surroundings.
What occurs when a car hits a wall?
Energy is transferred from the car’s kinetic energy store to other energy stores, including elastic potential and thermal energy.
What force acts when a car and wall touch?
A normal contact force acts on both the car and the wall.
What types of energy stores can be involved when a car hits a wall?
Kinetic energy, elastic potential energy, thermal energy.
Fill in the blank: Energy is ______ when a force moves an object.
transferred mechanically
What energy transfer occurs when wind causes a windmill to spin?
Describe the energy transfers occurring in the scenario.
How does stretching a spring affect energy?
The energy is stored as elastic potential energy.
What is the role of gravitational potential energy when an object is raised?
It is converted to kinetic energy as the object falls.
True or False: Energy can disappear during a transfer.
False
What is the significance of mechanical energy transfers?
They describe how energy is transferred through forces acting on objects.
What is the formula for kinetic energy?
Ek = ½mv²
Where Ek is kinetic energy, m is mass in kg, and v is velocity in m/s.
How do you calculate the kinetic energy of a car with a mass of 2500 kg traveling at 20 m/s?
Eₖ = ½ × 2500 × 20² = 500,000 J
This calculation shows how to apply the kinetic energy formula.
What is the formula for gravitational potential energy?
Ep = mgh
Where Ep is gravitational potential energy, m is mass in kg, g is gravitational field strength (9.8 N/kg), and h is height in meters.
What is the value of gravitational field strength on Earth?
9.8 N/kg
This value is used in calculations of gravitational potential energy.
What principle states that energy cannot be destroyed?
Conservation of energy principle
This principle applies to energy transfers between different stores.
When an object falls without air resistance, what happens to its gravitational potential energy?
Energy lost from the g.p.e. store = Energy gained in the kinetic energy store
This illustrates the conservation of energy in free fall.
What happens to energy when an object is stretched or squashed?
Energy is transferred to its elastic potential energy store
This concept applies to materials like springs.
What is the formula for elastic potential energy?
Eₑ = ½kx²
Where Eₑ is elastic potential energy, k is the spring constant in N/m, and x is the extension in meters.
What is the condition for the elastic potential energy formula to be valid?
The limit of proportionality must not be passed
This relates to the behavior of the spring material.
Fill in the blank: The energy in an object’s gravitational potential energy store is related to its height above the _______.
ground
This relates to how gravitational potential energy is calculated.
True or False: Energy can be created or destroyed in a closed system.
False
This statement contradicts the conservation of energy principle.
How do you calculate the speed of a 2.0 kg object dropped from a height of 10 m after falling 5.0 m?
Use energy conservation principles and kinematic equations
Assume no air resistance and apply relevant formulas.
What is power?
Power is the rate of energy transfer or the rate of doing work.
How is power measured?
Power is measured in watts.
What is one watt equivalent to?
One watt = 1 joule of energy transferred per second.
What is the equation for calculating power in terms of work done?
P = W ÷ t
What is the equation for calculating power in terms of energy transferred?
P = E ÷ t
If 8000J of work is done in 50 seconds, what is the power?
160 W
If a motor has a power of 200 W and lifts a stuntman for 30 seconds, how much energy is transferred?
6000 J
Why does a more powerful car reach the finish line faster?
It transfers the same amount of energy over a shorter time.
True or False: Energy transferred and work done are the same thing.
True
How can energy be wasted during transfer?
Some energy is dissipated as useless energy stores.
What is one method to reduce energy wastage?
Lubrication reduces friction.
What is thermal conductivity?
Thermal conductivity is a measure of how well a material conducts heat.
What are thermal insulators used for?
To reduce the rate of heat transfer.
Fill in the blank: Energy can’t be ______.
created or destroyed
What factors affect how quickly a building loses heat?
- Thickness of walls
- Thermal conductivity of materials
- Amount of thermal insulation
What is one way to improve a building’s thermal insulation?
Use materials with a low thermal conductivity.
What role does lubrication play in energy transfer?
It reduces friction, allowing more energy to be used effectively.
What happens when part of a material is heated?
The energy is transferred and the material eventually gets warmer.
What is the equation for energy transfer?
E = Px t
E = energy, P = power, t = time
What happens to energy during any energy transfer?
Some energy is always dissipated
This energy is often described as ‘wasted’ energy.
What is a common form of wasted energy in energy transfers?
Thermal energy stores
This refers to energy that is not usefully transferred.
When using a mobile phone, where does the energy come from?
Chemical energy store of the battery
Some energy is usefully transferred while some is dissipated as thermal energy.
What is the effect of friction in energy systems?
It causes some energy to be dissipated
Friction acts between all objects that rub together.
How can lubrication reduce energy waste?
By reducing friction between objects
For example, oil in machinery reduces friction.
What is thermal conductivity?
A measure of how quickly energy is transferred by conduction
Materials with high thermal conductivity transfer energy quickly.
What are thermal insulators?
Materials with low thermal conductivity
They reduce unwanted energy transfers by heating.
What factors affect how quickly a building cools?
1) Thickness of walls
2) Thermal conductivity of walls
3) Amount of thermal insulation
Thicker walls and low thermal conductivity reduce cooling rate.
Fill in the blank: Energy can’t be created or destroyed - only _______.
transferred
Energy exists in different forms and can be stored.
What is one way a builder could reduce the rate of cooling of a house?
Increase wall thickness or use thermal insulation
Building with materials of low thermal conductivity also helps.
What is the definition of efficiency in energy transfers?
The efficiency of an energy transfer is a measure of the amount of energy that ends up in useful energy stores.
Efficiency cannot be 100% because some energy is always wasted.
What is the first efficiency equation?
Efficiency = Useful output energy transfer ÷ Total input energy transfer
This gives efficiency as a decimal, which can be converted to a percentage.
How do you convert efficiency from a decimal to a percentage?
Multiply the decimal answer by 100.
For example, 0.8 × 100 = 80%.
What is the efficiency of a television that transfers 28,800 J of useful energy from a total input of 36,000 J?
80%
Efficiency = 28,800 ÷ 36,000 = 0.8.
What is the second efficiency equation related to power?
Efficiency = Useful power output ÷ Total power input
This is useful when you know the power values instead of energy.
If a blender is 70% efficient with a total power input of 600 W, what is the useful power output?
420 W
Useful power output = 0.7 × 600 = 420 W.
What are some examples of non-renewable energy resources?
- Fossil fuels
- Natural gas
- Coal
These are commonly used for energy generation and transportation.
What is a common use of natural gas in heating?
Natural gas is burnt to heat water in a boiler, which is then pumped into radiators.
This is a common method for central heating.
What should you do to avoid wasting energy?
Turn off devices like the TV when not in use.
This helps conserve energy and improve efficiency.
Calculate the efficiency of a motor that transfers 300 J of energy with 225 J going into kinetic energy stores.
Efficiency = 225 ÷ 300 = 0.75 or 75%
Efficiency is calculated as the useful output divided by the total input.
What is the useful energy transferred by a machine with a useful power output of 900 W and a total power input of 1200 W?
Useful energy = 900 W
This means the machine is effectively using 75% of its input power.
Fill in the blank: Some energy is always ______ when energy is transferred.
wasted
This is why no energy transfer can be 100% efficient.
True or False: The efficiency of an energy transfer can be 100%.
False
Because some energy is always wasted.
What are some renewable energy resources mentioned?
- Water waves
- Hydro-electricity
- Solar
These resources can be replenished.
