Warm-Up! If you push horizontally on your textbook with a force of 1-N to make the book slide at a constant velocity, how much is the force of friction on the book? Friday, October 26, 2012

Answer: 1-N force of friction in the opposite direction to the push. Question: If you push horizontally on your textbook with a force of 1-N to make the book slide at a constant velocity, how much is the force of friction on the book?

Class periods are abridged (about 30 mins each) Today's Plan: Class periods are abridged (about 30 mins each) We will finish the lab and turn in before you leave.

Friction Lab - Part B Procedure - Step 2 - You must test this out by actually dragging the cart at different speeds: fast vs. slow (Do not guess). - Step 4: Place a cart flat on the side with greater surface area (area of contact / configuration 1) and load it with 5- N of weight. Use the smooth wooden side, not rubber. - Then, drag it at constant speed and record the force of friction. - Step 5: Repeat Step 4 but use the narrow side of the block. Record the force of friction. Just indicate "area of contact" as large or small. Step 6: compute the coefficient of friction and complete Data Table B. (Don't confuse force with pressure!)

Analysis Questions Complete all analysis questions and have them ready to turn in by the end of the class period today. Notes & Hints: #4. If a number has many significant figures/digits past the decimal point, what does this say for accuracy and consistency in testing? What would this say about coefficients that cannot supply as many sig figs? #5. Pressing down is the same as adding extra weight and increasing the normal force. http://www.youtube.com/watch?feature=player_embedded&v=KEBJmZL8G1E