1. What is the coefficient of friction?
Do Now: DRAW FBDs
What affects the friction force between two objects, neglecting inclines?
How much force does it take to slide a steal beam over another at a constant speed if the beam has a mass of 1750 kg?
A man pushes a 40kg lawn mower with a 100 N force 30o above the horizontal at a constant speed.
What is the FF?
What is the coefficient of friction?

2. Aim: Review for Newton’s Laws and Friction Exam
HW: Study for Test using Review Sheet

3. Steps for Calculating Forces anywhere
Draw a FBD
Write sum of the forces and Newton’s law for each direction.
Sum of forces equal 0 if in equilibrium, but “ma” if there is a NET force or acceleration.
Solve for unknowns

4. Station Activity Go to your stations and attempt the problems given.
DRAW FBDs or you will lose A LOT of points!

5. Station 1
A 3.0-kg block rests on an incline that makes an angle 300 to the horizontal. a. Draw a FBD b. Determine the magnitude of the normal force. c. Determine the frictional force.
***Typical regents question

6. Station 2
I pull a 4 kg block to the right horizontally with a force of 20N. The force of friction is 4N.
Draw FBD
What is the Net force and block’s acceleration?
c. What is the coefficient of friction?

7. Station 3
Jack (60 kg) and Jill (50 kg) stand in the middle of an ice rink. Jill pushes Jack and he accelerates at 1.5 m/s2 away from Jill.
Draw a diagram
What force and acceleration does Jack have?
Explain their movement in terms of Newton’s 3rd law.
Who has the greatest inertia? Why?
What is the force due to gravity on Jill?

8. Summary
When is something in equilibrium? What does that mean for the forces involved?
What are the components of weight for an object on an incline. How do we solve for them?
3. What is the difference between static & kinetic friction?