## Sunday, January 16, 2011

### Round and Round and Round We Go!

This is what I learned about circular motion and gravity. I learned that in order for an object to be in any kind of circular motion, there needed to be some sort of centripetal force keeping the object moving in a circle. Whether the centripetal force is the friction between car tires and the road, or just the tension of a string swinging a ball, it is always there. I learned that the velocity is constantly changing when an object is in circular motion because the direction is always changing. I learned the Law of Universal Gravitation and how every object attracts every other object in the universe. I learned that the variable G is always $6.67x10^{-11}N.m^{2}/kg^{2}$. I also learned how to find the acceleration due to gravity in situations not on the earth's surface.
When we first started out this unit I had some difficulties understanding all of the concepts. I especially had trouble with figuring out which equation to use with the given information. It was very difficult for me to change equations in order to find different quantities. What I have found difficult about what I have studied is finding and using the sum of the forces equations when dealing with motion in vertical circles. I had lots of trouble figuring out how to use the sum of forces (sigma F) equations with the new equations we learned specifically for circles. The most difficult concept for me to comprehend was gravitational acceleration, specifically when we had to use ratios to find our answers. I eventually figured out how to use ratios in these cases and once I did everything became infinitely easier. What I found most simple was the whole concept of gravitational acceleration. The whole concept was easy to understand and made sense so it did not cause me much trouble.
My problem solving skills have definitely increased over the course of this unit. As usual, I started out the unit very confused and unsure how to solve most of the problems, but as I worked more problems and did the classwork in our notes, I became more confident. One of my weaknesses at the beginning was calculating the centripetal force when there is very little information given. Say you are in a car and about to enter a traffic circle with a radius of 30 m. You are traveling at 6 m/s and the mass of your car is about 300 kilograms. In order to find the centripetal force you would use the equation $F_{c}=mv^{2}/r$. Then you would plug in the information and you would get Fc=360 N. Now that seems fairly simple, but if you take away one of the variables and everything becomes much more complicated. I think the main thing that made this unit difficult for me was that for almost every single problem there was more than one step to find the answer and I would get confused on when to do what and how. Mostly all of the gravitational problems were fairly easy to comprehend. This unit has definitely helped me to better understand circular motion, gravitational acceleration and how forces are everywhere.