Science Test Notes

Questions and Answers

Energy can be destroyed but not created.

Energy is the ability to do work or cause change. (correct)

Energy is only present in kinetic form.

Energy can only be transformed, not transferred.

1 joule (correct)

1 kilojoule

1 kilocalorie

100 joules

It is energy of movement.

It is always wasted energy.

It can be converted into kinetic energy. (correct)

It cannot be used to do work.

1/2 x mass x speed^2 Signup and view all the answers

Kilojoule (kJ) Signup and view all the answers

Using less energy to perform the same amount of work. Signup and view all the answers

mass x gravitational field strength x height Signup and view all the answers

1 kcal = 4.2 kJ Signup and view all the answers

Study Notes

Energy is measured in Joules (J); 1 joule is used to lift an apple 1 meter.
Energy is typically recorded in larger units like kilojoules (kJ), where 1 kJ equals 1000 J.
Food energy is measured in kilocalories (kcal); 1 kcal is equivalent to 4.2 kJ.

Kinetic Energy: Energy of movement; associated with moving objects that produce heat. Calculated as:
- ( \text{Kinetic Energy} = \frac{1}{2} \times \text{mass (kg)} \times \text{speed}^2 )
Potential Energy: Stored energy; found in objects capable of doing work. Gravitational potential energy formula:
- ( \text{Gravitational Potential Energy} = \text{mass (kg)} \times \text{gravitational field strength (9.8 m/s²)} \times \text{height (m)} )

Energy can be transferred (moving from one entity to another) or transformed (changing types of energy).
Energy flow can be represented through diagrams, illustrating forms of energy and their transitions.

Efficiency refers to utilizing less energy to achieve work.
Input energy: Energy put into a system (e.g., chemical potential energy from petrol).
Output energy: Energy produced from the system (e.g., kinetic energy of a moving car).
Unwanted energy forms, like heat and sound, are considered waste.
Efficiency formula:
- ( \text{Efficiency} = \left( \frac{\text{Useful Output Energy}}{\text{Total Energy}} \right) \times 100 )
- Values must be in Joules or kilojoules, with results expressed as a percentage.