energy Flashcards
what is kinetic energy
kinetic energy is the energy stored in moving objects
what is the formula for kinetic energy
0.5 * mass * velocity^2
if a car is moving at 15 m/s with a mass of 900 kg how much kinetic energy does the car have
0.5900(15^2) = 101250
what is elastic potential energy
it is the energy stored in a spring when it is stretched
what is the relation between extension and the force applied to the spring
they are directly proportional until it reaches the limit of proportionality when the spring will eventually break (stretch without returning back to its original shape) this is the elastic limit of the spring
what is the formula for elastic potential energy (given in the exam)
Elastic potential energy = 0.5 * spring constant (N/m) * extension squared (m)
what is gravitational potential energy
it is the energy stored due to its position above the earths surface
what is the formula for gravitational potential energy
gravitational potential energy = mass(kg) * gravitational field strength (N/Kg and is 9.8 on earth) * height (m)
what is specific heat capacity
it is the amount of energy to raise the temperature of one kilogram of a substance by 1 degree Celsius
what is the the formula for specific heat capacity
change in thermal energy (J) = mass (kg) * specific heat capacity (J/Kg °C) * change in temperature
what is the Law of conservation of energy
Law of conservation of energy states that energy cannot be created or destroyed only transferred
what is a system
a system is an object or a group of objects
what is a closed system
in a closed system no energy can enter or leave
how can you reduce unwanted energy transfers in a cars wheel
by reducing friction which can be done using a lubricant or reducing the amount of air particles around the object
what is work
work is when energy is transferred from one source to another
what is mechanical work
it is using a force to move another object
what is electrical work
it involves a current transferring energy
what is the formula for work done
work done (J) = force (N) * distance (m)
what are the equations for power
Power (W) = energy transferred (J) / time (s)
Power (W) = work done (J) / time (s)
what is efficiency
it tells us what percentage of the energy we put into an appliance turns into useful energy
what are the formulas for efficiency
useful output energy transfer / useful input energy transfer
useful power output / useful power input
what is thermal conductivity
thermal conductivity relates to how easily energy is transferred by conduction through the material
what is the formula for change in thermal energy
change in thermal energy (J) = mass(Kg) * specific heat capacity (J/Kg°C) * change in temperature (°C)
how can heat loss be reduced
it can be reduced by using materials with low thermal conductivity
what is the specific heat capacity of a substance
it is how much energy is needed to raise 1 kg of it by 1 degree Celsius
what are the units of specific heat capacity
J/Kg°C
what is an independent variable
the variable that is changed
what is the dependent variable
the variable that is measured
what is the control variable
the variable that stays the same
what is the dependent variable
the variable that is measured
what are the advantages of fossil fuels
they are reliable and release a great amount of energy. Fossil fuels are abundant and cheap and are versatile (can be used in many places as they are portable
what are the disadvantages of fossil fuels
they release a lot of carbon dioxide, they are non renewable. they can release other pollutants such as carbon particles and nitrous oxides from diesel and sulfur dioxide from coal
what is nuclear power
it is a non renewable source of energy that comes from radioactive sources such as uranium and plutonium
what are the advantages of nuclear power
it does not release carbon dioxide and is very reliable
what are the disadvantages of nuclear power
it contains harmful radioactive materials and if there is an accident it can be dangerous to the environment surrounding it. Nuclear power plants take very long to decommission and also generates radioactive waste that needs to be stored for thousands of years
what are the advantages of gas fired power stations
they generate less CO2 than burning coal and are very flexible with a short start up time
