Chapter 3: Energy

Front

What is energy?

Back

Energy changes forms, but it is conserved. It cannot be made or destroyed.

Front

How long does it take for energy in sunlight to reach Earth's surface?

Back

8 minutes.

Front

What happens to sunlight when it reaches Earth?

Back

A lot of it is reflected back into space, some of it warms Earth, and much of it is absorbed by photosynthetic organisms like green algae.

Front

What do plants use the Sun's energy for?

Back

Plants use the Sun's energy to grow and create sugars and other materials.

Front

What happens to some algae and plants after they die?

Back

They build up at the bottom of the ocean or a swamp and over millions of years, transform into underground fossil fuel deposits.

Front

What is the role of refineries in energy conversion?

Back

Refineries use petroleum to create gasoline, which when burned, converts energy to power engines and rotate tires.

Front

What is the physicist's definition of energy?

Back

The ability to do work.

Front

What is work in physics?

Back

Work is done anytime a force is exerted over a distance. It is equal to the force exerted multiplied by the distance over which it is exerted.

Front

What is the formula for work?

Back

Work (joules) = force (N) x distance (meters). W = F x d.

Front

What are the units for force and work?

Back

Newton is the unit for force, and joule is the unit for work.