I was absent the class before this so I didn't get that packet.
Tuesday, November 25, 2014
Friday, November 14, 2014
Friction Lab
1. Surfaces pressed together
-Question: When the surfaces are pressed together harder, how does that affect the force of friction?
-Variables: Independent Variable- normal force
Dependent Variable- Friction
Controlled Variable: Velocity and surface and block?
-Prediction: I predict that when the objects are pressed harder together, the force of friction will increase.
-Apparatus: Block (rubber or Velcro)
Masses (Weight)
Machine that measures force (Ft)
Table (Fn)
Computer
-Procedure: Attach the block to the machine that measures force and start moving it at a constant speed. Then you start adding weight to the top of the block and move it at a constant speed. You do this again with even more weight added. Then you do this whole experiment over but do it on the other side of the block. All together you would do the experiment twice, once with the velcro and once with the rubber. You can tell the machine measures the force of friction because the force of friction and the power of the machine have to be equal because the block is moving at a constant speed. By adding weight you can tell the Fn because the weight you added equals the force of Fn because they are equal because it is not moving up nor down.
-Procedure: Attach the block to the machine that measures force and start moving it at a constant speed. Then you start adding weight to the top of the block and move it at a constant speed. You do this again with even more weight added. Then you do this whole experiment over but do it on the other side of the block. All together you would do the experiment twice, once with the velcro and once with the rubber. You can tell the machine measures the force of friction because the force of friction and the power of the machine have to be equal because the block is moving at a constant speed. By adding weight you can tell the Fn because the weight you added equals the force of Fn because they are equal because it is not moving up nor down.
DATA TABLE:
Velcro:NORMAL force
Natural Force (Newtons) Force of Friction (Newtons)
0.64 N 0.16 N
1.13 N 0.24 N
1.62 N 0.36 N
2.60 N 0.45 N
5.54 N 0.86 N
8.33 N 1.38 N
Rubber:
Natural Force (Newtons) Force of Friction (Newtons)
0.64 N 0.46 N
1.13 N 0.68 N
1.62 N 0.76 N
2.60 N 1.19 N
5.54 N 2.78 N
8.33 N 4.29 N
-Verbal Model: As the normal force increases, the force of friction increases proportionally.
-Math Model: Ff = (0.2 N/N) x Fn + 0.07 N
-Slope: For every one Newton added to the normal force, the force of friction increases by 0.2 Newtons.
-Y-Intercept: When the normal force is at 0 Newtons, the force of friction is at 0.07 Newtons.
-Verbal Model: As the normal force increases, the force of friction increases proportionally.
-Math Model: Ff = (0.5 N/N) x Fn + 0.02 N
-Slope: For every one Newton added to the normal force, the force of friction increases by 0.5 Newtons.
-Y-Intercept: When the normal force is at 0 Newtons, the force of friction is at 0.02 Newtons.
2. Velocity
-Question: How does the velocity affect the force of friction?
-Variables: Independent Variable: Velocity
Dependent Variable: Friction
Controlled Variable: Velocity the velocity can't be a controlled variable if it is one that you are testing. Controls are things that do not change in the experiment.
-Prediction: I predict that the faster the object is moving, the friction will be the same because the Fn is still constant.
-Procedure: Change the velocity of the block and pull it at different speeds. Then measure force of friction and see the relationship while using the same Fn and surface.
-Force of Friction vs. Velocity: We found out that the velocity does not affect the force of friction.
3. Surface area on ground
-Variables: Independent Variable: Velocity
Dependent Variable: Friction
Controlled Variable: Velocity the velocity can't be a controlled variable if it is one that you are testing. Controls are things that do not change in the experiment.
-Prediction: I predict that the faster the object is moving, the friction will be the same because the Fn is still constant.
-Procedure: Change the velocity of the block and pull it at different speeds. Then measure force of friction and see the relationship while using the same Fn and surface.
-Force of Friction vs. Velocity: We found out that the velocity does not affect the force of friction.
3. Surface area on ground
- Question: How does the surface area affect the force of friction?
-Variables: Independent Variable: Surface Area
Dependent Variable: Force of Friction
Constant Variable: Speed and Surface Materials
-Prediction: The larger the surface area is, the more friction there will be.
-Procedure: Measure the force of friction while using a piece of wood and using all the different sides to enable us to change the surface area. While the surface area is changing, the speed and surfaces still have to remain constant throughout the experiment.
-Surface Area vs. Force of Friction: The surface area does not affect the force of friction.
where is the graph I made for you?
Conclusion
-Introductory Paragraph: By doing these three experiments, we were trying to find out how the Fn, velocity, and surface area effects the force of friction. We found out that the only thing that effects the force of friction is the change in Fn and the surface. For all three experiments we kept the surface constant. In experiment one we changed the Fn, experiment two we changed the velocity, and in experiment three we changed the surface area and found out Fn was the only variable that changed the force of friction.
-Experiment One: All the graphs using the same surface are linear. When the surfaces are not pushed together there will be no force. The slopes are the same because the slope describes the type of surface and we all used the same surface. The slope for the velcro side was 0.2 N/N and the slope for the rubber side was 0.9 N/N. The slope for the velcro was less than the rubber side because velcro has less friction than rubber. The larger the slope, the more force of friction there is. The general weight of the block that was used was 65 grams. Since that was a general weight, it might have affected some of the graphs slightly, but the slopes were generally still the same.what is the slope called? what is the equation?
-Experiment Two and Three: For graphs for experiments two and three show that the velocity and surface are does not affect the force of friction. The force of friction will always remain the same if the Fn and surface remain constant even if the velocity or surface area changes. I predicted that the velocity would not effect the force of friction but the surface area would. I was correct about the velocity but wrong about the surface area. I thought since more area is touching the other surface, I thought that would increase the amount of friction.
-Drawing Conclusions: It is possible for two people wearing identical shoes to have different forces of friction because of the surface they are standing on and/or how much they weigh. One person could be standing on carpet and the other one could be standing on hardwood, which would effect the force of friction because the surfaces they are standing on are completely different. The weight could also change the amount of friction. This is like the experiment where the Fn was changed. Because the weight of the person is heavier, that causes more Fn since the force of gravity and the normal force are equal. The higher the Fn, the more friction there will be. yes....Two people have different types of shoes could have the same amount of friction because the the Fn could be equal and from the experiment about surface area, how would that make the same friction force then?we learned that surface area does not effect the amount of friction. In summary, the amount of friction force is caused by the amount of normal force and kinds of surfaces while the surface area does not affect the amount of friction force.
-Errors: Two sources of error that occurred during this experiment were that we forgot to zero the machine that measures the force of friction and in the first experiment when we were supposed to move the object at a constant speed. We could fix this by remembering to zero the machine and have something that moves at a constant speed drag it. Finding how the slope of the surface affects the friction would be interesting to learn.
-Journal Statement: I feel like I am getting better at lab reports because I feel like I know what information to put in and what the important information is. To improve my writing we could go over what should be in each part again.true, good job!
-Variables: Independent Variable: Surface Area
Dependent Variable: Force of Friction
Constant Variable: Speed and Surface Materials
-Prediction: The larger the surface area is, the more friction there will be.
-Procedure: Measure the force of friction while using a piece of wood and using all the different sides to enable us to change the surface area. While the surface area is changing, the speed and surfaces still have to remain constant throughout the experiment.
-Surface Area vs. Force of Friction: The surface area does not affect the force of friction.
where is the graph I made for you?
Conclusion
-Introductory Paragraph: By doing these three experiments, we were trying to find out how the Fn, velocity, and surface area effects the force of friction. We found out that the only thing that effects the force of friction is the change in Fn and the surface. For all three experiments we kept the surface constant. In experiment one we changed the Fn, experiment two we changed the velocity, and in experiment three we changed the surface area and found out Fn was the only variable that changed the force of friction.
-Experiment One: All the graphs using the same surface are linear. When the surfaces are not pushed together there will be no force. The slopes are the same because the slope describes the type of surface and we all used the same surface. The slope for the velcro side was 0.2 N/N and the slope for the rubber side was 0.9 N/N. The slope for the velcro was less than the rubber side because velcro has less friction than rubber. The larger the slope, the more force of friction there is. The general weight of the block that was used was 65 grams. Since that was a general weight, it might have affected some of the graphs slightly, but the slopes were generally still the same.what is the slope called? what is the equation?
-Experiment Two and Three: For graphs for experiments two and three show that the velocity and surface are does not affect the force of friction. The force of friction will always remain the same if the Fn and surface remain constant even if the velocity or surface area changes. I predicted that the velocity would not effect the force of friction but the surface area would. I was correct about the velocity but wrong about the surface area. I thought since more area is touching the other surface, I thought that would increase the amount of friction.
-Drawing Conclusions: It is possible for two people wearing identical shoes to have different forces of friction because of the surface they are standing on and/or how much they weigh. One person could be standing on carpet and the other one could be standing on hardwood, which would effect the force of friction because the surfaces they are standing on are completely different. The weight could also change the amount of friction. This is like the experiment where the Fn was changed. Because the weight of the person is heavier, that causes more Fn since the force of gravity and the normal force are equal. The higher the Fn, the more friction there will be. yes....Two people have different types of shoes could have the same amount of friction because the the Fn could be equal and from the experiment about surface area, how would that make the same friction force then?we learned that surface area does not effect the amount of friction. In summary, the amount of friction force is caused by the amount of normal force and kinds of surfaces while the surface area does not affect the amount of friction force.
-Errors: Two sources of error that occurred during this experiment were that we forgot to zero the machine that measures the force of friction and in the first experiment when we were supposed to move the object at a constant speed. We could fix this by remembering to zero the machine and have something that moves at a constant speed drag it. Finding how the slope of the surface affects the friction would be interesting to learn.
-Journal Statement: I feel like I am getting better at lab reports because I feel like I know what information to put in and what the important information is. To improve my writing we could go over what should be in each part again.true, good job!
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