Tuesday, January 26, 2010

Reflection: "Circular Motion and Gravitation"

I learned about circular motion, gravitation, and centripetal force. We learned before the difference between scalar and vector quantities, which comes in handy when it comes to centripetal force. Objects moving in a circular motion have a constant speed, but that doesn't mean the velocity will be constant since the object is changing direction. An object traveling at a constant speed in a circular motion is said to be in uniform circular motion. In order to obtain the velocity (m/s), one must figure out the distance and the period. To find the distance (around a circle's perimeter), you would use the equation: 2∏r. "T", the period, is the time that it takes to complete a full rotation. Also, an object is considered accelerating if it is changing direction. In circular motion, it's called centripetal acceleration. Acceleration is perpendicular to the velocity. Also, the inward force that keeps the object in a circular motion is known as the centripetal force. Moving on to universal gravitation, the Law of Universal Gravitation states, "Every object in the universe attracts every other object in the universe with a force that varies directly with the product of their masses and inversely with the square of the distance between the centers of the two masses." There is a lot to know about circular motion and gravitation!

What I have found difficult is drawing FBDs for objects in circular motion. I get confused as to where to place the arrow that describes where the acceleration is going. Also, I sometimes have finger problems when typing universal gravitation equations into my calculator. I believe that these difficulties can be solved over a short amount of time though.

I feel that my problem-solving skills are average. I definitely think that there is room for improvement though! On problems that aren't exactly like ones I have done before, I need to use similar skills used on previous problems rather than freaking out because I haven't seen anything like it. I feel that I am fairly good at figuring out the data I have and the data that I need to find out though. With some more practice, I can get my problem-solving skills to above average!

Sunday, January 10, 2010

Newton's Second Law

Part A:

I learned about Newton's Second Law about acceleration and forces. Newton stated that "for a particular force, the acceleration of an object is proportional to the net force and inversely proportional to the mass of the object." In an equation, this would be a=∑F/m, which could also be seen as ∑F=ma. Newton's Second Law provides a concrete connection between force and acceleration. Also, the directions of acceleration and the force are the same. Also, in this unit, we worked with friction a lot. In order to get the net force used in Newton's Second Law, we sometimes need to know friction. There are two types of friction, static and kinetic. Static friction occurs when objects are at rest, and kinetic friction occurs when an object is in motion. With this information, it was possible to solve problems pertaining to forces and acceleration.

What I have found difficult is knowing what equation to use. I find it challenging to set up an equation sometimes because it confuses me on when to set the equation to equal zero or m×a. Once I figure out the correct equation, though, I can solve the problem without much confusion.

I feel that my problem-solving skills are accurate enough to succeed in honors physics. In other words, my problem-solving skills are average. As mentioned in reflection 1, I sometimes get impatient and frustrated when I can't figure out how to solve a problem. I do, however, feel confident in drawing FBDs and solving for the unknown once I have figured out the equation to use. My weaknesses include occasionally forgetting to multiply the mass by 9.8 in order to get the weight of an object, or visa-versa. I do feel, though, that I can solve the majority of problems without a hitch.