Science Flashcards
What is potential energy?
This is stored energy. Such as
Gravitational potential energy (objects with
mass at a height)
Elastic Potential Energy (e.g., energy stored
in a spring)
Chemical Potential energy (energy stored in
chemicals e.g., food, battery, petrol)
Nuclear Potential
Magnetic Potential
What is active energy?
This is energy that is not stored that causes
movement (of waves or particles)
e.g., Kinetic energy,
Light energy, Electrical,
Heat, Sound
What are these types of energy?
Petrol in a car is……
Person running is …
Stretched rubber band is …
Burning match is …
Skydiver standing on a building
Petrol in a car - is…… Chemical potential
energy.
Person running is … Kinetic energy
Stretched rubber band is Elastic potential
energy.
Burning match is heat energy (and some
light energy)
Skydiver standing on a building =
Gravitational potential energy
Energy can be transformed from one type to
another.
When a battery is used to turn on a light bulb,
describe the energy transformations.
Chemical potential energy(battery)——> electricity ———> Light and heat (lightbulb)
When a skateboarder is standing on the top of
a hill and lets the skateboard move down it.
Describe the energy transformation.
Gravitational potential energy (top of hill)
——->Kinetic energy (moving)——–>heat and sound
(comes to a halt at bottom)
A light bulb uses 1500 joules energy to operate.
400 joules of energy is used for light every
minute.
How much wasted energy is there and where
does it go?
1500 – 400 =1100 joules of wasted energy
The wasted energy is heat-energy
State the law of conservation of energy.
Energy cannot be created or destroyed, it
can only be transformed or transferred.
Explain what the law of Conservation of energy
means?
The input energy must be the same as the
output energy.
It means when energy is transferred or
transformed, new energy is not created, nor
is energy destroyed.
If 2000 joules of input energy goes into the
system, then 2000 joules must go out of the
system as other forms of energy.
The formula for calculating Gravitational
potential energy is Ep = m g h
g = 10 N/kg
If 2000 kg is raised to a height of 10m.
What is its gravitational potential energy?
Always write the formula
Then substitute in
Ep = m g h
Ep = 2000kg x 10m x 10
= 200,000 J or 200 kJ (include units)
The formula for calculating Gravitational
potential energy is Ep = m g h g = 10 N/kg
If 30 kg is raised to a height of 50m.
What is its gravitational potential energy?
Always write the formula
Then substitute in
Ep = m g h
Ep = 30 kg x 50m x 10 N/kg
= 15,000 J or 15 KJ
A LED has electrical energy input of 1200
joules/seconds.
Light produced per second is 800
joules/seconds.
What is the energy efficiency percentage?
800/1200 x 100 = 66% efficient
(The times x 100 is to turn it into a
percentage)
What is energy efficiency?
How much of the input energy is
transformed to a useful form. Represented
as a %.
Energy used in everyday use.
For a car what is
Input energy =
Useful energy =
Input energy is Chemical potential energy.
Useful energy is Kinetic energy.
Energy used in everyday use.
For a radio plugged in at home what is
Input energy =
Useful energy =
Input energy = electrical
Output energy = Sound
What is the unit for energy?
Joules ( J )
1000 joules = 1 kilojoule (kJ)
