Honors Physics Sample Lab Report Conclusion- Friction Lab
-P1- What relationship exists between the variables? (provide a written statement and a math model)
The relationship between the perpendicular force of the surface and parallel force of the surface (We often refer
to this as friction, but friction is a very broad term referring to many different forces opposing motion, so never call it just
friction. Always be SPECIFIC about your forces) is that as the perpendicular force of the surface is increased, the
parallel force of the surface is increased this is shown in the equation below. F(parallel)surface= .3608*F
(perpendicular)surface
P1- What do the values of your slope(s) and intercepts(s) tell you about the relationship between
variables? Do the slope(s) and intercept(s) make sense (why or why not?) Use the 5% rule to determine
if the y-intercept should be zero (ONLY if that makes sense!)
The value of our slope tells us that in order to experience an increase in force of .301 N parallel to the surface
there must be an increasing force of 1 N in the perpendicular direction. We did not have a y-intercept because
if there is no force being applied perpendicular to the object then there should not be any force parallel either.
In our case we had a y-intercept of zero and it was correct because there is no reasonable explanation for
there to be a y-intercept if no force is being applied parallel to the object.
P1- What are the general meanings of the slope(s) and intercept(s)? Is there a general formula that can
be created from your math model?
The slope tells us how much an object’s force in the direction parallel to the surface (its force of friction) will
increase if 1N of force is added in the direction perpendicular to the object. The y-intercept is simply error in the
data. There are two general formulas that can be created from the math model, which are:
F(surface parallel)=uk* F(surface perpendicular)
F (surface parallel)= us*F(surface perpendicular)
(Notice in this section, they didn’t use their specific slope numbers when talking about the GENERAL meaning of the
slope. In the previous section they did)
P2- Do the class results support your claims? What caused different groups to get different results?
Every group had similar graphs for pulling the motion detector were similar: they had an initial “max” force and,
after the object began moving, the force reading decreased and evened out. However, the graphs of the
parallel and perpendicular forces had slopes that differed because we all used different masses and some
people used either the wood block or metal block. In addition, the force people used to pull the blocks varied
depending on the person pulling.
P2- Define any new terms that were defined in the class discussion.
Coefficient of Kinetic Friction: the relationship between the perpendicular force and frictional force when an
object is moving.
Coefficient of Static Friction: relationship between the perpendicular force and frictional force when an object is
not in motion.
Friction: the parallel force on an object caused by contact with a surface
P3- Does the body of scientific work support your claim(s)?
The body of scientific work does support our claim that when an object initiates movement, the frictional force
is greater than when an object is moving. This is shown through our graphs of force vs. time as the block was
pulled. Our results also show that there is a linear relationship between the perpendicular and parallel forces of
the surface acting on an object.
P3-Are there any differences between your claims and those of the scientific community? Explain why
any differences exist and calculate the % error.
**Only do this section when there is one correct answer (ex: the acceleration due to gravity should ALWAYS be
9.81)**
P4- Address strengths, and/or weaknesses of the experiment. How could you improve the experiment?
Throughout the lab, we might have had various errors that could have occurred. Some of our weaknesses
were that we didn’t pull the string attached to the block with a steady velocity for all the trials. It was really
difficult to pull the block with a steady or constant velocity. Also, there was sometimes (I changed “might have
been” to sometimes because you don’t want to write about errors you MIGHT have had. I want to know what errors you
DID have!) a delay from the time we pressed the start button, which impacted our data slightly. On the other
hand, one of our strengths was that we had success in collecting data which was shown by the consistency of
our graph shapes. If there’s anything that I believe that we could have improved throughout our experiment is
to pull the rubber band attached to the block with more care and steadiness or attach the rubber band to a cart
or machine that can pull the block at a constant velocity.
P5- How is what you learned from this lab useful or where is it applies in everyday life? (Make me care!
This should be important!)
Friction in fact, always opposes movement. Why then is friction necessary? For walking and keeping a car on
the road. For example, if the car’s tires were perfectly smooth and to make matters worse, the road was
perfectly smooth as well. The vehicle would keep moving forward when the driver attempted to stop. For this
reason, tires are designed with raised thread to maintain high degree of friction. Also the force of friction makes
it possible for the tires to turn themselves.
***(This is NOT a good example! I want something INTERESTING! We discussed companies and industries that might
car about this in class. Ex: Race car drivers and engineers. The coefficient of friction between a tire and the road makes a
big difference for a driver trying to win a close race. Do some research on a topic and write about it. The more specific the
better!)