Friction is a force that works against motion between two surfaces that are touching. Sometimes this is because two surfaces are rough and don't slide easily. If a surface isn’t smooth, there’s sliding friction, which is influenced by the mass of the moving object and the smoothness of the surface it’s moving on.

Question

Rolling friction is usually less than sliding friction, which is why it's easier to move heavy furniture on a hand truck. Rolling friction happens when we use wheels.

Fluid friction makes it difficult to move through liquids like water. It's also the friction caused by air on the outside of a moving vehicle. You can feel fluid friction on your face when you run against the wind.

Which of the following best describes how friction affects motion?

A
Friction makes motion between two touching surfaces much easier.

B
Sliding friction makes running on a windy day much harder on your body.

C
Rolling friction makes moving through liquids feel like very hard work.

D
Friction makes motion between two touching surfaces more difficult.

Answer 1

The option that best describes how friction affects motion is:

D Friction makes motion between two touching surfaces more difficult.

This option accurately reflects the general principle of friction, which opposes motion between surfaces in contact.