Friction Lab

CALENDAR NOTE: Forces Test on Monday. Make sure to practice the CONCEPTS we've been talking about (fight with those pesky componant problems!). Also, please bring in a sample AP multiple choice problem (regarding forces) that we chan chew on tomorrow (Friday). Googling AP Physics C released tests will provide way, way, way more information than you need!

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INVESTIGATIVE QUESTION:

Can we determine the material our desktops are made from using a wooden block, a ruler, an electronic scale and a timing mechanism?

Consider the following situation:

Object A is a block of wood provided to you.

Object B is a weight of known mass.

When object B is attached as shown, it drags the wooden block across the desk as it falls towards the center of the Earth under the influence of gravity. The block resists that motion.

Please make sure that the following steps (1-5) are included in your 'sample calculations' section as-is (don't clean them up).

1. Sketch that situation in your notes . Do NOT proceed until you have a working apparatus built. That is to say your sketch should be what engineers call an "As Built" diagram. All appropriate distances and dimensions should be labeled but need not be to scale (You'll do that later as indicated below).
2. Draw a free body diagram for each mass.
3. Do a 'sum-of-the-forces' analysis on each.
4. Write an equation that describes that situation.
5. Using all your physics acumen(!) derive an equation that will allow you to solve that equation for μ. (HINT: You'll need to determine a method for *precisely* measuring the acceleration of the wooden block. (Did I mention that you MUST use calculus in conjunction with your collected data?). Oh, by the by, you MUST use calculus in conjunction with your collected data to find acceleration).

Discuss with your crew how you will use your calculations and data to find (or try to find) the material that makes up our desk tops.

Your lab report MUST also include an "As-Built" diagram to scale. That means you may NOT free-hand the drawing. Use a straight edge as appropriate. Also, all distances and dimensions MUST be drawn to scale (really).

There is a VERY good chance that the μ that you find will contain error... you'll need to do a % error calculation on that:

(|Actual Value| - |Experimental Value|) / (Actual Value)

and then discuss that in the error section of your report. Note, you'll still need to track error propagation in your other calculations, this is a separate and distinct error analysis.

NOTE: Best error analysis will NOT focus on human error but will instead focus on physics issues inherent in the lab.