Chapter 2- Energy Stores And Equations Flashcards
Kinetic energy of an object
The kinetic energy (KE) of an object (also known as its kinetic store) is the energy it has as a result of its speed
Kinetic energy equation
KE= 1/2 x m (mass) x V squared (velocity/speed)
What happens when an object is lifted up or down
If an object is lifted up, it will gain GPE. If it falls, it will lose GPE
Equation for gravitation potential energy (GPE)
GPE= m (mass) x g/10n/kg (gravitational field strength) x h (height)
What is the gravitation field strength (g) on the earth
10 n/kg
What happens when a string is stretched or compressed
Work (energy) is done on the spring which results in a transfer of energy to the springs elastic store
Elastic potential energy (E) equation (the work done on the spring ,, which is equal to the amount of energy stored)
E = 0.5 x spring constant x extension squared or E = kx(squared sign)
What is the specific heat capacity of a substance
It’s the amount of thermal energy needed to raise the temperature of 1kg of that substance by 1 degree Celsius
Specific heat capacity equation (the amount of thermal energy needed to raise the temperature of a given mass of material by a different amount)
Change in thermal energy = mass x specific heat capacity x change in temperature (in joules) or E = m x c x (triangle symbol delta)T
What units does specific heat capacity have
Joules per kilogram per degree Celsius (J/kg ^C)
How do you calculate power (P)
P = W/t (work done divided by time taken)
Unit of power
Watt (W), which is the same as a joule per second (J/s)
What is (the) power
Machines, like car engines, transfer energy from one type to another every second. The power is the amount of energy they transfer each second
If two identical cars accelerate to the same final speed and one of them reach that speed sooner, what will it have
It will have the greater power
Energy efficiency equation
Efficiency = useful energy transferred by the device divided by the total energy supplied to the device
