Unit Reflection:
In unit 4 we learned about torque, rotational and tangential
speed, rotational inertia, center of mass, center of gravity, centripetal
force, and centrifugal force. To start this section we learned about rotational
speed, which is the number of revolutions that are made in a certain amount of
time, and tangential speed, which is the distance covered in a certain amount
of time. We learned that while two people on a merry go round may have
different tangential speeds, they would both have the same rotational speed. We
applied our knowledge of tangential speed to roller derby and discovered that
the purpose of “the whip” move is so that the skater being whipped could gain a
greater tangential speed and therefore pass her opponents. Similarly we leaned
that if you increase the size of your tires on your car you could be driving at
a faster speed than your speedometer reads. An objects angular momentum has to
do with how much mass is closer or further form the axis of rotation. An object
with a larger amount of mass away from the axis of rotation is going to move
slower than if the mass was closer to the axis of rotation. An object with more
mass further away from the center is going to have a greater rotational inertia
because it is going to be more difficult for the object to begin to move. If
the mass were more towards the center however, the object is going to have a
lower rotational inertia and be easier to begin moving. Next we learned about
torque and center of mass. Torque causes rotation. Torque = lever arm X force.
The longer the lever arm that you are using to turn an object the smaller force
you are required to apply and vice versa. We then learned that because of
center of mass, when we put on our backpacks, we subliminally lean foreword so
we don’t fall. Because we increase our mass behind our natural center of mass
we need to lean foreword and balance out our new center of mass. This action
keeps us form falling over. As long as our center of mass remains under us we
will stay standing. We also learned that the leaning tower of Pisa does not
fall over because its center of gravity is being supported by it’s base. In
other words the center of gravity is within the base of support. We then moved
on to centripetal and centrifugal forces. Centripetal force is the center
seeking force when you are turning on a curve in your car. The feeling of fling
that you feel when you are turning on this curve is the centrifugal force. The
center fleeing force you feel is the fictitious force. We learned that during
the spin cycle when your clothes are in the washing machine, the water leaves
the basin through little holes not because of a force but because of a lack of
force present. Personally, I struggled with this unit more than I have with the
others. Coming and asking questions in the morning would have been beneficial.
