James investigates which type of material has more frictional force on a ball. He chooses concrete, carpet, wood flooring, and grass as his different materials. He describes the texture of each of these materials with words such as hard, soft, rough, and smooth. Before he rolls the ball on the material, the ball rolls down a ramp. This is done to make sure that the ball rolls with the same amount of force.

Question

What are the controlled variables? Select all that apply.

material of floor

the ramp

type of ball

how far the ball travels

Answer 1

material of floor
the ramp