Science

Question 1

What is potential energy?

Answer 1

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

Question 2

What is active energy?

Answer 2

This is energy that is not stored that causes

movement (of waves or particles)
e.g., Kinetic energy,
Light energy, Electrical,
Heat, Sound

Question 3

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

Answer 3

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

Question 4

Energy can be transformed from one type to
another.
When a battery is used to turn on a light bulb,
describe the energy transformations.

Answer 4

Chemical potential energy(battery)——> electricity ———> Light and heat (lightbulb)

Question 5

When a skateboarder is standing on the top of
a hill and lets the skateboard move down it.
Describe the energy transformation.

Answer 5

Gravitational potential energy (top of hill)
——->Kinetic energy (moving)——–>heat and sound
(comes to a halt at bottom)

Question 6

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?

Answer 6

1500 – 400 =1100 joules of wasted energy
The wasted energy is heat-energy

Question 7

State the law of conservation of energy.

Answer 7

Energy cannot be created or destroyed, it
can only be transformed or transferred.

Question 8

Explain what the law of Conservation of energy
means?

Answer 8

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.

Question 9

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?

Answer 9

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)

Question 10

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?

Answer 10

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

Question 11

A LED has electrical energy input of 1200
joules/seconds.
Light produced per second is 800
joules/seconds.
What is the energy efficiency percentage?

Answer 11

800/1200 x 100 = 66% efficient
(The times x 100 is to turn it into a
percentage)

Question 12

What is energy efficiency?

Answer 12

How much of the input energy is
transformed to a useful form. Represented
as a %.

Question 13

Energy used in everyday use.
For a car what is
Input energy =
Useful energy =

Answer 13

Input energy is Chemical potential energy.
Useful energy is Kinetic energy.

Question 14

Energy used in everyday use.
For a radio plugged in at home what is
Input energy =
Useful energy =

Answer 14

Input energy = electrical
Output energy = Sound

Question 15

What is the unit for energy?

Answer 15

Joules ( J )

1000 joules = 1 kilojoule (kJ)

Question 16

What is renewable energy?

Answer 16

Renewable energy is defined as energy that
is collected from resources that will never
run out or which are replaced by nature in
less than a human lifetime.

Question 17

What is non-renewable energy?

Answer 17

Non-renewable energy is defined as energy
collected from resources that cannot be
replaced when they are used up, such as oil,
natural gas, or coal.

Question 18

Examples of renewable and non-renewable
energy sources in New Zealand?

Answer 18

Renewable: Hydroelectric energy, solar
power, wind turbines, geothermal energy,
biofuel energy.
Non-renewable: Fossil fuel, nuclear energy,
natural gas, coal.

Question 19

Pros and Cons of hydroelectric power
generation?

Answer 19

Cons: Damage to the estuary habitats and
damage to valley habitats by flooding.
Pros: Cheap to run (no fuel costs) and no
polluting gasses produced.

Question 20

Define energy

Answer 20

Energy is defined as ‘the ability to do work’. The simplest way to think about it is the ability to make something
happen, change or move.