1. Home work: Finish the worksheet #16
Aim: What happens to friction as the angle of incline increase?
Do Now: Fill the chart below:
Home work:
Finish the worksheet #16
The angle ()
The sine of 
The cosine of  0° 1 30
0.5
0.866 45
0.707 60 90

2. Conceptual
A teapot is initially at rest on a horizontal tabletop, then one end of the table is lifted slightly. What happens to: Explain your answer
The normal force
Increase
Decrease
Remain the same
The Force of Friction
Increase
Decrease
Remain the same

3. Activity Everyone stand up and rub your hands against reach other.
What do you observe?
How can this be detrimental to machinery?
How can engineers remedy this consequence?
Talk about machinery and putting oil to lubricate and reduce friction.

4. Friction is FUN
FF = μ FN
The force of friction is equal to the coefficient of friction multiplied by the normal force.

5. Do Now
If two wooden boxes 30 kg wooden boxes attached with a string are pulled across a wooden floor.
Draw the free body diagram.
Find the magnitude of all the forces acting on it.
How does the Force of friction compare to the force applied?
If the sting is cut what will happen to the boxes?
Calculate the acceleration of crate.

6. Inclined plane Practice
Calculate the amount of force required to overcome the force of friction between: A box of steel of 20kg down a steel surface inclined at 30º. How much force would be required to keep the motion?

7. FN Fg FF
F applied
A 35 kg is accelerating down an incline of 25° and is pulled with a force of 185N the kinetic coefficient of friction is 0.27.
What is the acceleration of the box?
Draw the free body diagram.

8. F pull= 185N, θ=25°, m= 35kg, μ K = 0.27. a=? FN= mg cos θFg FF
F applied
FN= mg cos θ
(35kg)(9.8m/s2) cos(25°)= N
FFK = μ K FN
(310.86N)(0.27)=83.93N
a= F net/m
a = (185N-83.93N)/35kg = 2.9m/s2

9. Homework
Up a ramp of θ = 12°, start at rest pulled at an angle of 25° with respect to the incline with force of 185N, what’s the a=? μ K = 0.27. FN Fg FF
F applied
FN= mg cos θ
(35kg)(9.8m/s2) cos(12°)= N
FFK = μ K FN
(335.50N)(0.27)=90.59N
a= F net/m
a= (185Ncos(25°)-90.59N)/35kg = 2.2m/s2

10. Homework m= 75kg, down a ramp of θ = 25°, a= 3.60m/s2. μ K = ?,
If m = 175kg, then a=?

11. Homework
W= 325N, constant velocity, F applied = 425N downward at an θ = 35.2° below the horizontal, μ K = ?

12. How much force is required to get a copper container of 15kg on steel counter top to start to move? Keep it moving? If a 50 kg wooden crate is pulled with a horizontal force of 150N across a wooden floor. Describe what happens to the crate.

13. Compare and Contrast
In 3 to 5 sentences, use the knowledge of forces, and physics terms. May include a chart comparing the distance traveled, the force exerted, the angle and other variables. Include free-body diagrams