October 16 (Tuesday) Friction is Fun Lab Day 1
If you were gone today:
The Einstein Board:
1. Is It Possible? Roller-coaster Man video
2. Reminders that the 40 pt. Balloon & Bottle Lab is due this Friday as is all the Problem Set for Unit 2 (1-10) also the GNATS Multiplying extra credit is due this Friday.
3. LAB GROUPS - Juniors stood who would be gone tomorrow for the PSAT test and made sure they were in the groups of three or did not group together at least. Everyone else picked a new partner.
4. f = u N LAB Explanation on the Smart Board period 7
5. f = u N LAB the rest of today and tomorrow.
Note: A setup will be back in the resource area if you wish to make up the
f = u N Lab. We had mainly groups of two with students choosing someone they have never had for a partner yet. This is a quickie lab in that you need not do a purpose, procedure, or conclusion or summary but need to fill in the data tables and answer all the questions. The exploratory Friction Lab Handout
This is an exploratory lab meaning it is designed for you to figure out for yourself some facts about friction before just being told. Even if you missed today, read through the below and imagine when you get back going through these five steps. Thursday we will go through factors that affect friction but it is fun to try to figure them out yourself during this lab today and tomorrow. Remember tomorrow is an early release day.
Consider the following possibilities for friction discoveries:
1). At the exact point (the instant before the object starts to move) where the object starts to move NOTE the force on the spring loaded force scale; does the scale reading go down or up at the instant the object starts at a constant speed sliding. The actual number is not as important as noticing if the reading goes down, goes up, or stays the same for all three different surface pairs.
2). Try two very different constant speeds (real slow and moderately fast (slow enough to get a reading on the scale your pulling with) across the same part of the surfaces. Note: the center may be smoother due to decades of use so try the back side or not the middle of the front side. Also, wipe off the surfaces before starting with a cloth.
3). Try pulling the object on its side (where the surface area touching is less but the weight of the object over this lesser surface area is more force pushing the two surfaces together compared to the more surface areas in contact with less force (weight of object) pushing the surfaces areas together. Do you see much of a difference in the force readings?
4). Try adding a small, medium, and large mass (1/4 kg, 1/2 kg, 1 kg) to the object. How did this affect the force reading on the scale to pull the object at a constant speed?
5). Calculate using f = u N solving for mu gives u = f / N where f is the reading from the spring scale and N equals the total weight in Newtons of the object your pulling with the weight sitting on top from step 4. Note the three coefficients of friction (u). Did the coefficient of friction for the same surfaces in contact change much even though you added a small, medium, and heavy weight to the object?
Consider the following possibilities for friction discoveries:
1). At the exact point (the instant before the object starts to move) where the object starts to move NOTE the force on the spring loaded force scale; does the scale reading go down or up at the instant the object starts at a constant speed sliding. The actual number is not as important as noticing if the reading goes down, goes up, or stays the same for all three different surface pairs.
2). Try two very different constant speeds (real slow and moderately fast (slow enough to get a reading on the scale your pulling with) across the same part of the surfaces. Note: the center may be smoother due to decades of use so try the back side or not the middle of the front side. Also, wipe off the surfaces before starting with a cloth.
3). Try pulling the object on its side (where the surface area touching is less but the weight of the object over this lesser surface area is more force pushing the two surfaces together compared to the more surface areas in contact with less force (weight of object) pushing the surfaces areas together. Do you see much of a difference in the force readings?
4). Try adding a small, medium, and large mass (1/4 kg, 1/2 kg, 1 kg) to the object. How did this affect the force reading on the scale to pull the object at a constant speed?
5). Calculate using f = u N solving for mu gives u = f / N where f is the reading from the spring scale and N equals the total weight in Newtons of the object your pulling with the weight sitting on top from step 4. Note the three coefficients of friction (u). Did the coefficient of friction for the same surfaces in contact change much even though you added a small, medium, and heavy weight to the object?
Here is this years version of the Friction is f = u N Lab and questions to be answered.
Enjoy the lab!