#Goals: SWBAT...
1. Describe which friction coefficient refers to moving objects, and which refers to objects at rest
2. Draw accurate FBD's
3. Solve problems involving kinetic and static friction
Warm-Up (5min)
Copy the following, then draw the FBD and list all the given and unknown information.
CLASSWORK
1. #035A: An Example of how to solve a Friction Problem, plus some Practice Problems
A. We will solve the warm-up problem together, then you'll solve a few problems on your own
Take notes as we solve
B. Solve these on your own:
Theory Problem:
1. Would the friction between a tire and the road be increased by a wide rather than a narrow tire? Explain.
Math Problems:
2. Mr. Ames is dragging a box full of books from his office to his car. The box and books together have a combined weight of 134 N. If the coefficient of static friction between the pavement and the box is 0.55, how hard must Mr. Ames pull the box in order to start it moving?
3. Suppose that a 52N sled is resting on packed snow. The coefficient of kinetic friction is only 0.12. If a person weighing 650 N sits on the sled, what force is needed to pull the sled across the snow at constant speed?
At Home Learning (HW)
1. Complete the problems from #035A
Want to know more about why the tire question answer is what it is?
http://www.physlink.com/education/askexperts/ae200.cfm
If you're stuck, I'll post some solutions here by the end of the school day
2. #035B: Watch/take notes/complete edPuzzle on the following:
(8:59) Determining the Static Coefficient of Friction between Tires and Snow - EDpuzzle
3. #035C: Work on your problem solving skills by solving this problem. (The video above shows a similar problem, but you'll need to use a different UAM equation to solve this problem.)
4. Derek is playing cards with his friends, and it is his turn to deal. A card has a mass of 2.3 g, and it slides 0.35 m along the table before it stops. If the coefficient of kinetic friction between the card and the table is 0.24, what was the initial speed of the card as it left Derek’s hand?