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P1 - Conservation and dissipation of energy - Coggle Diagram
P1 - Conservation and dissipation of energy
Energy Stores
Types of energy stores
Elastic potential energy stores describe the energy an object because it is being stretched or squashed
Kinetic energy stores describe the energy an object has because it is moving.
Chemical energy stores include fuel, foods, and the chemical found in batteries.
Gravitational potential energy stores describe the energy an object has because of its position relative to the ground.
Thermal energy stores describe the energy an object has because of its temperature
Energy can be transferred from one store to another
Energy can be transferred by heating, waves, an electric current, or when a force moves an object
When an object fall and gains speed, its gravitational potential energy store decreases and its kinetic energy store increases.
When a falling object hits the ground without bouncing back, kinetic energy store is transferred by heating to thermal energy store of object and surroundings, & by sound waves moving away from the point of impact
Energy dissipation
Wasted energy is energy that is not useful energy and is transferred by an undesired pathway.
Wasted energy is eventually transferred to the surroundings.
Useful energy is energy in the place we want it and in the form we need it.
As energy dissipates it gets less and less useful.
Gravitational potential energy stores
It's equal to the work done by the lifting force.
Work is done on it to overcome the gravitational force.
If an object is moved upwards, the energy in its gravitational potential energy store increases.
If an objects is moved downwards, the energy in it's gravitational potential energy store decreases.
The gravitational field strength at the surface of the Moon is less than on the earth.
It's equal to the work done by the gravitational force acting on it.
The gravitational energy store of an object increases when it moves up and decreases when it moves down.
E = m x g x h
Change in the gravitational potential store = mass x gravitational field strength x change of height
E - change in gravitational potential store - J
m - mass - kg
g - gravitational field strength - N/kg
h - change in height - meters
Conservation of energy
A closed system is an isolated system where no energy transfers take place out of or into the energy stores of the system.
When a person stretches an elastic band, the chemical energy store of the person muscles decreases and the elastic potential energy store of the elastic band increases.
Energy can be transferred usefully, stored or dissipated.
When an object falls freely, the gravitational potential energy store decreases and the kinetic energy store increases.
Conservation of energy is
Energy cannot be created or destroyed - applies to all energy changes.
Energy can be transferred between different stores within a closed system. The total energy of the system is always the same, before and after transfers.
Energy and work
Energy transferred = work done
Work and energy both have the unit joule, J
When a force moves an object, energy is transferred to the object and work is done on it.
Friction - force that opposes the motion of two surfaces in contact with each other.
Work is done on an object when a force makes the object move.
Work done to overcome friction is transferred to thermal energy stores by heating.
If an object does not move when a force is applied to it, no work is does on the object.
W = F s
Work done = force x distance
W - work done - J
F - force - N
S - distance moved in the direction of the force - meters
Kinetic energy and elastic energy stores
The energy in kinetic energy store of moving object depends on its mass & speed.
Elastic potential energy is energy stored in elastic object when work is done on the object.
Elastic potential energy stored in a stretched spring.
Ee - elastic potential energy - J
k - spring consistent of the spring - N/m - newtons per meter
Ee=1/2xkxe2
e - extension of spring - m
Kinetic energy store
Ek = 1/2 x m x v2
Ek - kinetic energy - J
m - mass - kg
v - speed of an object - m/s
Energy and efficiency
No energy transfer can be more than 100% efficient.
Machines waste energy because of friction between their moving parts, air resistance, electrical resistance and noise.
The efficiency of a device = useful energy transferred by the device / total energy supplied to the device x 100
Energy supplied to a device is input energy
Energy transferred usefully by the machine is called the useful output energy.
Electrical appliances
Uses of everyday electrical appliances include heating. lighting, making objects move, and producing sound and visual images.
An electrical appliance is designed for a particular purpose and should waste as little energy as possible.
Electrical appliances can transfer energy in the form of useful energy at the flick of a switch.
Electricity, gas and/or oil supply most of the energy used at home.
1.9 - Energy and power
Power of an appliance
P=E/t
P - power - W
t - time taken for transfer - s
E - energy transferred - J
Efficiency of an appliance = useful power out/ total power in x 100.
Power is rate of transfer of energy.
Power wasted by an appliance = total power (input)- useful power (output)