Energy Flashcards
What are the 7 different energy stores?
Chemical
Kinetic
Gravitational Potential
Elastic Potential
Thermal
Magnetic
Nuclear
How can energy be transferred?
Heating, waves, electric current or force
What is the name of the energy stored by a moving object?
Kinetic
What happens to dissipated energy?
It spreads out to the surroundings
What is the equation for kintetic energy?
1/2 x mass x velocity^2
What is the equation for gravitational potential energy?
mass x gravity x height
What is the equation for elastic potential energy?
1/2 x spring constant x extension^2
What is the principle of conservation of energy?
Energy cannot be created or destroyed.
What does the conservation of energy apply to?
all energy changes
What is meant by a closed system?
No energy transfers take place out of or into the energy stores of the system.
Complete the sentence: Energy transfers can take place between ___________ __________ within a ___________ _________.
energy stores, closed system
True or false : The total energy of a closed system is never the same before and after energy transfers.
False
What is work done?
Energy transferred when an object is moved by a force.
What is the equation linking force, work done and distance moved?
work done = force x distance moved
What is work done to overcome friction transferred as?
energy to the thermal energy stores of the objects that rub together and to the surroundings
What happens to the gravitational energy store of an object when its height increases?
Increases
What is the gravitational field strength on earth?
9.8N/kg
How many grams in 1kg?
1000g
What does the kinetic energy of an object depend on?
Its mass and speed
What is elastic potential energy?
The energy stored in an elastic object when work is done on it.
What is Hooke’s law?
Force = spring constant x extension
What is useful energy?
energy transferred to where it is wanted in the way it is wanted
What is wasted energy?
energy that is not usefully transferred
What is the most common energy store of wasted energy?
Thermal
What is the equation for efficiency?
efficiency = useful output energy/ total input energy x100
True or false: No energy transfer can be more than 100% efficient.
True
What are the 4 reasons why devices waste energy?
friction, resistance of a wire, air resistance, sound
How can friction be reduced?
Lubricate the moving parts
How can the resistance of a wire be reduced?
use wires with little electrical resistance
How can air resistance be reduced?
Use streamline shapes
How can sound be reduced?
cut out noise
What is the wasted energy of a light bulb?
thermal
What is the wasted energy of an electric heater?
sound and light
What is the wasted energy of an electric toasted?
thermal heating the air around it