Name:______date:______period:______(3)

Science 8: Ch 12.3 Friction: A Force that Opposes Motion (pages 350-355)

Key Concept
Friction is a force that can ______other forces to prevent ______. Friction is also a force, that when ______, can change the ______of an object.
What stops a ball from continuing to roll away from you?
Define friction.
What can friction do to an object?
Are surfaces of any object rough?
The hills and valleys covering the surface of even the smoothest objects stick to what?
The magnitude of friction between two objects depends on what? / 1.
2.
What can increase the friction between the surfaces of two objects?
Which produces less downward force, objects than weigh more or objects that weigh less?
Looking at Figure 2, which book, heavier or lighter, is harder to push across the table?
Does the amount of surface touching another surface affect the amount of friction?
In which situation is friction the greatest, between materials that have a rougher surface or between materials with a smoother surface?
In which situation is friction larger, a table-tennis ball rolling on carpet or rolling on a wood floor?
What are the two types of friction? / 1.
2.
What is an example of kinetic friction?
What is an example of static friction?
What does the word “kinetic” mean?
What are two ways surfaces can move? / 1.
2.
Which of the two ways surfaces can move has greater friction?
What are three examples of how you use kinetic friction everyday? / 1.
2.
3.
Does kinetic friction usually act on balanced or unbalanced forces?
Can kinetic friction cause a change in velocity?
What does kinetic friction do to a moving object?
How can static friction be overcome and an object starts to move?
Once an object starts to move, what type of friction is it?

Using Figure 4 on page 353, show how kinetic friction replaces static friction. Be sure to use force arrows correctly.

Looking at Figure 4, which letter (a, b, or c) shows balanced forces on the object?
How does a ladder leaning against a wall not move?
How can friction be harmful?
How can friction be helpful?
Define lubricant
What are two examples of lubricants? / 1.
2.
What is an example of a gas lubricant?
How do ball-bearing reduce friction?
How can sanding down a wood bench reduce friction?
What is one way to increase friction?
Why does a batter where gloves?
Looking at Figure 6 on page 355, how is friction increasing?