Wednesday, January 27, 2010

Reflection: Gravitational forces, Centripetal forces, and Circular motion

I learned a lot about circular motion, gravitation, and centripetal force. I learned that uniform circular motion is when the object is moving at a constant speed in a circle. The velocity is found by 2pi(r)/T. T is the period, or the time it takes for the object to complete one full revolution around the perimeter of the circle it is going in. When an object changes direction, it accelerates. So although the object may have a constant speed, it does not have  constant velocity (scalar vs. vector!). The velocity is tangential, and the acceleration of the velocity is called centripetal acceleration. This is found by the equation v^2/r. The acceleration is perpendicular to the velocity. The force that keeps the object going in a circle is called centripetal force. This force is found by using mv^2/r. There are also vertical circles. These circles are not much different, accept for at the top you subtract mg and when it is at the bottom you add mg. Universal Gravitation states that the force that pulls all other bodies and causes them to fall exists also between all other bodies. This force pulls down, but also things together. This helps things like the planets stay in orbit.

What I have found difficult is knowing what equation to use at what time; especially with the gravitational equations. I also find the FBD's difficult to draw, because the forces can be switched around. I also sometimes get confused what the system is. I am still getting the hang of gravitational forces, but i think i am getting better. Practice makes perfect.

I think that my problem solving skills are pretty good, but could definitely improve. I think that with the more problems that I see, I improve with each one. I sort of freak out when I glance at a problem and it seems too difficult. But when I actually look at it and focus I usually see a way to find the answer. I think my problem solving skills are definitely improving.


  1. Good reflection!
    Please be careful with spelling (title should say gravitational) I is capitalized, nto should be 'not', " Gravitation states that states ", perhaps you should work on a word document first and then copy it here..
    You seem to imply that the centripetal force is a special kind of force, is that true?

  2. what do you mean? about the centripetal force? it sort of is, because it is the force that pulls things inward and keeps them in a circle, but sort of no, because it is just the same force.. i am kind of confused. and do i change something to fix that ?

  3. Kelly,
    I agree, good reflection! I also struggle with the "freaking out" part, but what I have found to be the best thing to do is to find someone who understands it (my person is Michael from Texas who is assigned with Ian), and have them explain it to me in a way that I understand. Oftentimes when a teacher goes over example problems, they seem so simple at the time, yet impossible when doing them alone.
    Also, you mentioned some excellent things that I had not thought of before in terms of the centripetal. However, keep pondering on the question from dgende.
    Good job!