Download Static Friction Problems

4.3 Solving Friction Problems
Static Friction Problems
• If two or more objects are attached, you must overcome the combined maximum
force of static friction to cause the object to move.
• Static friction can also be used to make an object move.
When you take a step forward, the bottom of your shoe is at rest with respect to
the ground. Your foot is not moving with the rest of your body. The reaction force
of static friction by the ground pushes you forward, allowing you to move.
SP # 1 p.173-174 – Static Friction on more than on object
SP # 1 p.175 – Static Friction causing an object to move
4.3 Solving Friction Problems
Kinetic Friction Problems
• When an object slides across a surface, kinetic friction acts on the object opposite
the direction of motion.
• One common misconception is that kinetic friction always reduces the net force
acting on the object.
If a person pushes against a sliding object to stop it from sliding any farther, both
the applied force and kinetic friction work together in the same direction increasing
the net force acting on the object.
SP # 1, 2 p.176
4.3 Homework
Day 1
Practice # 2 p.174
Practice # 1, 2 p.175
Practice # 1, 3 p.177
Day 2
Questions # 2, 5, 7, 9, 10 p.178