Things I learned this Unit:
Rotational Motion
Tangential speed- the distance an object covers in a given time. Depends on radial distance.
Rotational speed- the amount of rotations or portion of a rotation an object performs in a given time
Gears: Same tangential
speed, the smaller gear will have to have a faster rotational velocity
to account for the equivalent tangential speed.
Example- 8 teeth vs 4 teeth.
Smaller gear will have twice the rotational velocity as the bigger one
because it has to rotate 2 times to go the same distance it takes the
bigger gear to rotate once.
DIFFERENT RADIUS FROM AXIS OF ROTATION= DIFFERENT TANGENTIAL VELOCITY
Rotational Inertia + Conservation of Angular Momentum
Rotational inertia- property
of an object to resist changes in the spin. Distribution of mass affects
RI. Easier to spin= less rotational inertia, harder to spin= more
rotational inertia.
The greater the distance a mass is from its axis of rotation, the more rotational inertia it will have.
Angular momentum before= Angular momentum after
RI x RV before= RI x RV after
A hoop will have more
rotational inertia than a steel ball because its mass is further from
its axis of rotation, it will therefore lose a downhill race. (same goes
for frozen water bottle vs water bottle)
Torque and Center of Mass
Torque- something that causes a rotation, = Force x Lever Arm
Lever arm- the distance from an object's axis of rotation.
When an object is balanced its counterclockwise torque is equal to its clockwise torque
Center of mass- average position of mass
An object will fall when its center of gravity is outside of its base of support
Examples of torque + center of mass problems:
Why are football players told to keep their legs bent and shoulder width?
To widen their base of
support and get their center of gravity closer to the base of support,
they will then have to be pushed harder to get their center of gravity
outside of their base of support and fall.
Large wrench= more torque
10 N ball rests on one end of
a meter stick with a 1m lever arm. How much must a ball on the other
side weigh if it is 5m away from its axis of rotation?
10 x 1= 10
10/5= 2N
Centripetal Force
Centripetal force is a center seeking force
Centrifugal force does not exist
Why are racetracks banked?
So that they can have more centripetal force from the x component of the support force coming from the track.
In this unit I had difficulty with the concept of the racetrack being banked, but after being shown the force vectors I felt completely fine with the subject. I overcame this difficulty by learning to think of force vectors whenever provided such a picture.
My Problem Solving Skills, Effort, and Learning
Throughout the unit my problem solving skills improved by learning to think of things in different ways such as in force vectors or as in centripetal forces interacting with objects in the world. My effort in the class has been fairly consistent with a few dips in effort due to the fact that I grasped the material sooner than classmates and waited for them to see the reasoning behind a problem.
My goal for next unit is to have my effort back to where it was before.
My previous goal of not procrastinating has improved greatly and I often feel better prepared for class.
This unit helps me understand why in football I have to keep my legs spread out and my knees bent as to not be hit over so easily.
My group's unit podcast
I really loved the organization in this post. Everything was super easy to follow and the podcast was good.
ReplyDeleteSomething that was similar to mine was the fact that everything remained in order from what we learned first to what we learned by the end. But something that was different was that your this post did not include any pictures or diagrams to reference to. This could be something you could do next time, just to have a visual.