Which statement best describes what energy is?

A liquid that flows from hot objects to cold ones The ability to do work, or to cause a change in a system A force that pushes objects forward The weight of an object multiplied by its speed

What is the SI unit of energy?

Watt (W) Newton (N) Joule (J) Calorie (cal)

You push a heavy box across the floor. Energy is transferred from you to the box. What do we call this transfer of energy by a force acting over a distance?

Power Work Momentum Pressure

A book sits on a high shelf and has not moved for years. Does it have energy?

No — only moving objects have energy No — it has no energy because no work is being done on it right now Yes — it has gravitational potential energy due to its height above the floor Yes — but only if it is made of a heavy material like iron

The total amount of energy in a closed system always:

Increases when you add more objects to the system Decreases slowly over time because of gravity Stays the same — it transforms between forms but is never created or destroyed Doubles every time energy is transferred

A kettle heats water from cold to boiling. Which statement correctly describes what has happened to energy?

New thermal energy has been created inside the heating element Electrical energy has been transformed into thermal energy in the water The water gains mass, which is where the extra energy comes from Chemical energy from the plug socket enters the water

Which of these everyday situations involves the most obvious energy transformation?

A rock sitting still on a table A torch converting stored chemical energy in its batteries into light and heat A cup of water at room temperature An empty balloon left in a room

What is the difference between energy and power?

They are the same thing measured in different units Power is always greater than energy in any real system Energy is the total amount of work done; power is how quickly that work is done Energy is measured in watts; power is measured in joules

James Prescott Joule's most important discovery was that:

Heat always flows from cold objects to hot ones Mechanical work and heat are equivalent forms of the same thing — energy Energy is destroyed whenever a machine slows down Heavier objects have more energy than lighter ones at the same speed

You eat a meal and then go for a run. Which best describes the sequence of energy transformations?

Kinetic energy (running) → chemical energy (food) → thermal energy Thermal energy (body heat) → chemical energy (food) → kinetic energy Chemical energy (food) → kinetic energy (movement) + thermal energy (body heat) Nuclear energy (from food) → kinetic energy (movement)