Physics P1 Flashcards
What is energy ?
Energy is the ability to do work
What are the units for energy ?
Joules
What are the 5 most common energy stores ?
Chemical , kinetic , Gravitational potential , thermal and elastic potential.
What is a chemical energy store ?
The energy stored in chemical bonds molecules
What is an example of a chemical energy store?
A battery or fuel.
What is a kinetic energy store?
The energy of a moving object
What is an example of kinetic energy store ?
Buses , cars and runners .
What is Gravitational potential energy store?
The energy of an object at height.
What is a thermal energy store?
The total energy of particles in an object.
What is an example of a thermal energy store ?
Hot coffee or a radiator
What is elastic potential energy store ?
This is the energy stored when an object is stretched and squashed .
What is a magnetic energy store ?
The energy stored when repelling poles have been pushed closer.
What is an electrostatic energy store ?
The energy stored when repelling charges have been moved closer.
What is a nuclear energy store ?
The energy stored in the nucleas of an atom .
How do we increase an energy store ?
Energy must be transferred between stores
What are the five types of energy transfer?
Heating
Electrical
Light
Sound
Mechanical
What is the definition of the energy transfer heating ?
The transfer of heat energy from a hotter object to a cooler object.
What is the mechanical energy transfer ?
The transfer of energy through the movement or actions of objects.
What is electrical energy transfer ?
The transfer of energy through the flow of electric charges in an conductor.
What is the conservation of energy ?
Energy cannot be created or destroyed it can only be transferred from on store another .
What is a system ?
A system is a chosen object or a group of objects.
What is a closed system ?
A closed system is an isolated system in which no energy transfers take place into or out of the system .
What is work ?
Work is the amount of energy transferred when a force moves. Like pushing or pulling something.
What is the difference between work and energy ?
Work is the effort it takes to move something against a force and energy is the ability to do work , like fuel .
What is the equation for work done ?
Work = force x distance
Calculate the work done when a person applies a force of 15 N to move a box moving it 2 metres?
15 x 2 = 30 J
What is friction ?
Friction is a contact force that opposes the direction of movement when two surfaces are in control .
What is gravitational potential energy ?
Gravitational potential energy is the energy stored in an object due to its position above the Earths surface .
How do you calaculate the gravitational potential energy ?
GPE = mass x GFS x height
What is gravitational field strength ?
This is a measure of the force of gravity .
A crane lifts a 75 kg mass a height of 8m . Calcualte the gravitational potential energy gained by the mass ( g = 9.8 N/kg ).
75 x 9.8 x 8 = 5880 J
What is the definition of kinetic energy store?
The amount of energy an object has as a result of its mass and speed .
What is the equation for kinetic energy ?
Kinetic energy = 1/2 x mass x speed squared .
Calculate the kinetic energy stored in a vehicle of masd 1200 kg moving at a speed of 27 m/s.
Mass = 1200 kg
Speed = 27 m/s
Kinetic energy = 1/2 x 1200 x ( 27 ) squared.
= 440,000 J
What is Elastic potential energy ?
The energy stored in an elastic object when work is done on the object .
What does the definition of the elastic potential energy store mean ?
It means that any object that can change shape by stretching, bending or compressing
What is an example of elastic potential energy ?
When a spring is stretched work is done on the spring which results in energy being transferred to the elastic potential store of the spring . When the spring is released, energy is transferred away from its elastic potential energy store.
What is the equation for Elastic Potential energy ?
EPE = 1/2 x N x extension
Do you convert the units given in a question related to elastic potential energy to metres ?
Yes always
What is useful energy ?
Useful energy is energy transferred to where it is wanted and in the form it is wanted .
What is wasted energy ?
Wasted energy is energy not usefully transferred.
What happens to wasted energy ?
Wasted energy is eventually transferred into the surroudings .
What is wasted energy also known as ?
Dissipated energy
Why is it important to not waste energy ?
Because sometimes energy can be used for something else and the wasted energy can’t get reused.
What is the efficiency of a system ?
Its the measure of the amount of wasted energy in an energy transfer .
What is efficiency ?
The ratio of the useful energy output from a system to its energy input.
What is one equation for efficiency ?
Useful output energy transfer / total input energy transfer
A blender converts 700 J of energy into 150 J of useful energy .
150 /700 = 0.21
How can we improve the efficiency of a device ?
We can do this by reducing the wasted energy transfers and increasing the useful energy transfers .
What is power ?
The rate at which energy is transferred .
What is power measured in ?
Watts
What is the equation for power ?
Power = Energy transferred / time
What is another equation used to find power ?
Power = Work done / time
Is energy transferred and work done the same thing ?
Yes
How is power described ?
How fast the energy is transferred from one store to another .
Calculate the energy transferred when an iron with a power rating of 2000 W is used for 5 minutes .
- 2000 W and then covert 5 minutes in to seconds so 5 x 60 = 300 s
- Rearange the equation - power x time = energy
- 2000 x 300 = 600,000 J
9
The amount of energy required to raise the temprature of 1kg of a substance by 1 degrees .
