Energy Flashcards
Energy is _______ between stores
transferred
When energy is transferred to an object, energy is…
stored in of the object’s energy stores
When a system changes, what happens?
Energy is transferred
What is a system?
An object or group of objects
What are closed systems?
Systems where matter and energy cannot enter or leave
What is always the net change in total energy of a closed system?
Always 0
A simple pendulum has what type of motion?
Oscillating motion
In a simple pendulum, what is the energy transferred between?
Kinetic energy and gravitational potential energy
Work done = ___ ______
Energy transferred
Give 3 examples of work being done
- Initial force excerted by person to throw a ball upwards does work
- Friction between car’s brakes and its wheels does work (as car slows down)
- Collision between car and stationary object = normal contact force between car and object does work
What is the energy transfer for when a person throws a ball upwards?
Chemical energy → Kinetic energy
What is the energy transfer for when a car brakes?
Kinetic energy → Thermal energy
What is the energy transfer for when a car collides with a stationary object?
Kinetic energy → Elastic potential + thermal energy + sound energy
Energy can be ______ usefully, _____ or _______
Energy can be transferred usefully, stored or dissipated
Energy cannot be ______ or _____
Created or destroyed
Less energy that’s ‘wasted’, more _____ device is
efficient
Name 3 ways we can improve the efficiency of energy transfers?
- Insulating
- Lubricating
- Streamlining objects
How do friction and air resistance dissipate energy?
By heating the surroundings
How can the flow in a system be represented?
By using Sankey diagrams
Energy in kinetic energy store depends on object’s _____ and _______
mass and speed
Greater an object’s mass + faster it’s going, the more
kinetic energy it has
Raised objects have…
gravitational potential energy
Higher the object raised = the more
gravitational potential energy / energy transferred to its store
Stretching can transfer energy to ____ _______ ______ stores
elastic potential energy
What is power?
The rate of energy transfer OR the rate of doing work
1 Watt = …
1 joule of energy transferred per second
What makes a machine powerful?
If it can transfers a lot of energy in a short space of time
What is conduction?
Process where vibrating particles transfer energy to neighbouring particles
In conduction, how is energy transferred to object?
By heating
In conduction, what store of an object is the energy transferred to?
Transferred to its thermal store & shared across kinetic energy stores of particles
In conduction, what happens to particles when they’re heated up (mention collsions + how it leads to conduction)?
- Particles heated vibrate more and collide with each other
- These collisions cause energy to be transferred between particles’ kinetic energy stores
- = conduction
What is thermal conduction?
A measure of how quickly energy is transferred through a material
What do materials with high therma conductivity do?
Transfer energy between their particles quickly
What is convection?
Where energetic particles move away from hotter to cooler regions
In convection, how is energy transferred to object?
By heating to thermal store of liquid or gas
Why can metal conduct heat?
Particles are tightly packed and have free electrons which can move and carry heat
What do insulators do?
Reduce heat movement by conduction
Illustrate the particle arrangement in a conductor
Illustrate the particle arrangement in a insulator
Explain why insulators do not conduct heat easily
- Particles not tightly packed and there’s massive spaces between them
- ∴ When particles vibrate = vibrations (heat energy) cannot be passed onto nearby particles easily
Explain why hot air is more dense
- Heated particles move faster and space between individual particles increase
- Causes density of region being heated to decrease
Why does warmer and a less dense region (particles) rise above a denser, cooler region (particles)? (simple answer)
Because fluids can flow
When is a convection current created?
If there’s a constant heat source
