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Conceptual Physics Friction Lab Pre Lab: 1. Discuss with your group what factors you think affect the magnitude of the Force of Friction. Discuss how you think those factors will affect the magnitude. For instance, if you think that the height of the object affects the Force of Friction, discuss if you think the taller objects or the shorter objects have more friction. In your notebook, write down the factors your group thinks affects friction and how they affect friction. 2. Draw this diagram (you do not need to draw the hand) and label the forces acting on the block in your notebook.
Purpose: To determine what factors of an object’s motion affect the force of friction. Materials: String long enough to wrap around the block A variety of different surfaces that can be wrapped around the block Force scales that measure in Newtons Wood blocks (4-5 of the same size) Wood board to create a uniform surface Experiment #1: Nature of surfaces 1. Find your first data table labeled “Experiment #1: Nature of Surfaces” and notice that the title of the first column is “Surface,” and the second “Force Applied (N).” You will list the five surfaces you will be testing in the first column. Try to use descriptive terms that describe the type of material, its colors, etc. so that you can differentiate between them. 2. Place your block (largest side down) on the wood board and wrap the string around your block so that the block can be pulled along the board. 3. Attach the force scale to the other end of the string and pull it parallel to the table top. If it is pulled at an angle it will not correctly measure the force applied. 4. Pull the block at a constant velocity; you will know it is at a constant velocity if the magnitude of the force remains constant as you pull it and the velocity is relatively slow. Record this value of the force you applied in your data table for the surface (in this case “plain wood”). 5. Wrap one of the other surfaces underneath the block so that it is secure to the block. You should be able to tuck the surface underneath the string that is around the block. The surface needs to stay with the block while it moves and not impede its motion.
6. Repeat step #4 and record the force for this surface in your data table.
7. Replace the surface again and measure the force required until your data table is full for a total of five different surfaces. Experiment #2: Surface Area 1. Find your second data table labeled “Experiment #2: Surface Area” and notice the title of the first column is “Surface Area (cm2)” and the other “Force Applied (N).” 2. Return your block to its initial position with the largest side on the wood board and the string wrapped around it. 3. Notice that there are two different sides to a block, a smaller end, and the larger side of the block. Measure and calculate the surface area of each side of the block and record these measurements for surface area in your data table in cm2. 4. Measure the force necessary to pull the block at a constant velocity for each of these sides. Be sure to hold the scale parallel to the tabletop, as you did before. You will have to rearrange your string for each side. Experiment #3: Type of Motion 1. Find your third data table labeled “Experiment #3: Type of Motion” and notice that the title of the first column is “Type of Motion” and the other “Force Applied (N).” 2. Return your block to its initial position with the largest side on the wood board and the string wrapped around it. 3. Try pulling the block very slowly at first and measure the Force needed to just get it moving. You should see a large spike before its moving consistently, this is the force you are looking for. 4. Now try pulling the block in uniform motion (constant velocity as before) and measure the Force needed to move it at a constant velocity. 5. Write an observation about the force required to complete these two different motions in your lab notebook. Experiment #4: Speed of Motion 1. Find your fourth data table labeled “Experiment #4: Speed of Motion” and notice that the title of the first column is “Relative Speed” and the other “Force Applied (N).” 2. Return your block to its initial position with the largest side on the wood board and the string wrapped around it. 3. Pull the block at a constant slow velocity and measure the force needed to do so. 4. Restart the block in its original position and pull the block again at a constant velocity that is slightly faster than in your previous step and measure the force needed to do so. 5. Restart the block in its original position and again pull it at a constant velocity but this time at a constant velocity that would be considered fast. Take care though as you are accelerating a block in close proximity to other students. Experiment #5: Amount of mass 1. Find your fifth data table labeled “Experiment #5: Amount of Mass” and notice that the title of the first column is “Number of Blocks” and the other “Force Applied (N).” 2. Return your block to its initial position with the largest side on the wood board and the string wrapped around it. 3. Determine the force needed to pull one block at a constant velocity. Record this value in the table for one block. 4. Repeat step #3, adding a second block on top of the first. You will not move the string on the first block. Record the value of the force in the data table in your lab notebook. 5. Continue to add one block at a time and record the force necessary to pull it at a constant velocity.
