2.7 The Effects of Friction

_____________ friction prevents an object from moving.

• Static

• Kinetic

• Personality

• Jedi

________ friction opposes an object's movement while the object is moving.

• Static

• Kinetic

• Personality

• Jedi

Friction is

• always helpful

• always harmful

• sometimes helpful and sometimes harmful

Which is an example of harmful friction?

• salt on the sidewalk during the winter

• extra grip on tires during the winter

• extra grip on tires during the summer

• static friction while walking

Which is an example of helpful friction?

• bearings that reduce friction in machinery

• extra grip on tires during the summer

• rough contact between a sliding door and the floor

• dragging a heavy box along a rough floor

Friction

• augments motion by acting in the same direction

• augments motion by acting in the opposite direction

• opposes motion by acting in the same direction

• opposes motion by acting in the opposite direction

Starting friction is important because

• you have to start somewhere!

• you have to overcome it in order to move an object.

• it is the friction that all other frictions are based on.

• without starting it, you can't finish it.

What are some common types of friction? Select all that apply.

• sliding friction

• rolling friction

• water friction

• magic friction

• air friction