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.

Sunday, January 10, 2010

Newton's Second Law part A

I learned how to do many things after learning Newton's second law.  Newton's second law states, "for a particular force, the acceleration of an object is proportional to the net force and inversely proportional to the mass of the object." This law links mass, acceleration, and the forces. This can be used with many problems, and even systems. Systems don't usually balance out, and this law helps find the acceleration. This law uses the formula a=∑F/m or ∑F=ma. Using this formula I learned to solve problems with acceleration in them, not just problems at constant speed or at rest. I also found out how to solve systems, including problems using pulleys and Atwood's machines. With these problems I improved my ability to draw FBD's and calculate the sum of the forces. I have also learned how to calculate the friction force acting on an object. The equation for this is Ff= Fn(mu). mu is the coefficient of friction and is used to calculate the frictional force.

What I have found difficult with this law and these problems is when I do not have much information, and I  have to keep working on the problem and it somehow works out in the end. I get a little confused going through the problems without knowing multiple variables. Also, a am not quite a master at finding the mu and friction force, because we just learned about it and it is still fairly new.

I think my problem solving skills are improving and I am able to catch on to new ideas faster. Although I am not a master at the frictional force equation and problems yet, I am catching on to this idea much faster and already understand it with most problems. I sometimes find certain acceleration problems difficult when not much information is given. I am fairly secure with systems, and can usually find the answers that I am looking for. Overall I think I am getting better at solving problems and can grasp ideas quicker.