A. Explain how Newton’s first, second laws, and Third Laws apply to the performance of a car.
Newton’s
first law states that that every object continues in a state of rest or of
uniform speed on a straight line until acted on by a non-zero force. This connects
to the performance of a mousetrap car because while the car was placed at the
line, with the mousetrap set, it was at rest. It did not move until acted on by
a non-zero force. This force was the mousetrap when it was set off. This
non-zero forced caused the car to be set in motion. Newton’s second law states
that the acceleration produced by a net force on an object is directly
proportional to the magnitude of the net force, is in the same direction as the
new force, and is inversely proportional to the mass of the object. This has
something to do with the mousetrap cars because if the net force, strength of
the pull of the trap, was weak then the acceleration of the car was weak. If
the pull was very strong, like the one in Meredith and Isabelle’s car, then the
result will be a super fast acceleration like theirs was. Newton’s third law
states that whenever one object exerts a force on a second object, the second
object exerts and equal and opposite force on the first. This connects to the
performance of a mousetrap car because when the CD wheels are pushing off of
the ground, the ground is also pushing off of the CDs. Likewise, when the trap
pulls the string, the string pulls the trap.
B. What are the two types of friction present? What problems
related to friction did you encounter and how did you solve them? How did you
use friction to your advantage?
The two
types of friction present in this experiment were: The friction between the
string and the axis, and the friction between the CDs and the ground. Friction was a bigger problem then anyone
thought. In our first car, the string did not have great friction with the
axis. It would slip and slide on the axis and barely pull it with the amount of
force expected. There was not enough friction in that instance. In our second
car, friction was great. The string had great friction against our metal axis.
It pulled the axis with the expected force and allowed our car to go five
meters. We basically solved the friction problem by luck. Spontaneously building
a new car with a different axis helped conquer our friction problem. The
friction between the CDs was not as difficult as a problem to overcome. We
simply just put cut up balloons around the edges of the CDs so that they
wouldn’t slide on the tile floor. One
way that we used friction to our advantage was by adding more to the back
wheels and giving the front wheels as little as possible. This helped because
with the added friction on the back wheels, it made the car more capable of
receiving the greatest push possible. By leaving the front wheels naked, we
allowed the to just roll as fast as they could. If there were balloons around
the front wheels it would also just slow our car down.
C. What factors did you take into account to decide the
number of wheels? What kind of wheels did you use in each axle? What is the
effect of using large or small wheels?
When
choosing the number of wheels we really didn’t take much into account. We
honestly just thought about how most car wheels systems operate and worked off
that. That took us to our decision of four wheels. Stability though, is a huge
factor when choosing the number of wheels. We used CDs and DVDs. They are both
very slick circles with a hole great for the placement of an axel. We found out
that DVDs weigh more than CDs so we placed those in the back and put the CDs in
the front. This was helpful because you want more weight in the back where the
speed is delivered from, while you want the lighter wheels in the front so that
they don’t slow down the car. All of our
wheels were the same size. The benefit of using large wheels was that they were
better if you wanted to go long distances, while small wheels were better for
faster rotations and smaller distances.
D. Discuss the conservation of energy in how it relates to
your car? Be sure to include information about how your car’s use of potential
and kinetic energy.
The
conservation of energy states that energy cannot be created nor destroyed. This
means that all of the energy our car had was used in some way. When the car is
at rest with the trap not set it has no potential energy. When the trap is set
and the car is at rest it, then does have potential energy. This is because now
that the trap is set, energy is in a stored state. When released the car will now have kinetic
energy. Kinetic energy= ½ mass x speed. When the car gains speed it then gains
kinetic energy. Due to the conservation of energy all of the potential energy
will eventually be transferred to another form of energy. In our experiment,
that transfer was to kinetic energy and thermal energy.
E. What was the length of your lever arm? Discuss the effect
of the length of the lever arm in the a.
the pulling of the force and b. the power output of your car.
We added no
lever arm to our working car. We realized by trail and error and help from the
UNCA student. He said, “the longer the lever arm, the longer the distance.”
That might have been true, but it did not work for us. Also a longer lever arm
increases the torque of the car. So in our second attempt at a car we did not
add a lever arm. The lack of an extended lever arm allowed the force from the
trap to be delivered to the car faster. I honestly have no clue how a shorter
lever arm worked over the longer one. One problem we came across with the
longer lever arm was that is made our car unbalanced, which led to the change
in direction of our first car.
F. What role did rotational inertia, rotational velocity,
and tangential velocity play in your functioning car?
All three
of these factors played a huge role in our functioning car. Rotational inertia
is the property of an object to resist changes in its rotational state of
motion. If there had been no friction, no matter how slow our car would have
been, it still would have gone the required distance because there was no
outside force stopping it. Rotational speed and Tangential speed were the same
for both sets of wheels. They wheels we
used were the same size, therefore their rotational speed would result
in the same number of rotations in any certain unit of time. The tangential
speed is directly proportional to rotational speed. If our wheels had the same
rotational speed, they would also have the same tangential speed, which is the
direction of motion that is tangent to the circumference of a circle.
G. Why can’t we calculate the amount of work the spring does
on the car? Why can’t? t we calculate the amount of potential every that was
stored in the spring and the amount of Kinetic energy the car used? Why can’t
we calculate the force the spring exerted on the car to accelerate it?
We can’t
calculate the amount of work the spring does on the car because we don’t know
the amount of force that the spring acts on the car with. Also we can’t find
the change in Kinetic Energy either. We can’t calculate how much potential
energy was stored in the string because 1. We just don’t know how much force
the string is holding, 2. The car is not elevated, therefore we cannot figure
out the potential energy it holds. We can’t tell the Kinetic energy the car
used because we didn’t even know the potential energy. According to the
conservation of energy, no energy is destroyed or created. Therefore all that
potential energy would come out as Kinetic energy and heat. We can find the
kinetic energy at one point, but it would be irrelevant because we don’t know
the potential energy.
REFLECTION
A. How did your final design compare to your original
design? What prompted the changes?
Well our first design was stellar.
It worked the first time we tried it and so we left it alone for the weekend,
came back, and it wasn’t working. We tried so many things like adding a lever
arm, straightening the wheels, adding more and less rope but nothing worked.
For some crazy reason, I spontaneously just built a new car. Our old one was
frustrating so i made a new one not to
beat the old one but just to relieve stress. I like to build. Turns out that
that car was the one that work and went five meters the first time I tried it.
We made a few adjustments to keep the front wheels straight. Also we taped the
string to the back axis just so that coiling it would be easier.
B. Discuss major
problems encountered in the performance of your car and what did you do to
solve them?
I simply
built a new car that worked. When I say we tried everything on our first car
and nothing worked that I exactly what happened. We did everything and changed
everything possible. Building a new car was our last resort and sort of our
only option. The biggest problem was the fact that we started early and
finished our project. We were so content that we had completed it way before
everyone. We enjoyed our weekend and then came back to a nonfunctioning car. To
solve this we spent countless hours working in the lab to fix it. Nothing
worked and that lead us to the construction of a new car.
C. If you were to do this project again, what would you do
differently in the future that could make you car fast?
I would
make everything as small as possible. Is seemed the faster cars were the ones
with the least amount of added items. Isabelle and Meredith used the trap as
their chassis and that is why they were the fastest. Everything must be small,
I would even make smaller CDs. I am actually going to build another mouse car
just because I know I have the potential to make a car as fast as theirs.
