In this unit I learned about Newton's second law of motion and about the force of friction. Newton's second law states the for a particular force, the acceleration of the object is proportional to the net force and inversely proportional to the mass of the object. The direction of the force is the same as that of the acceleration. In equation form this is simply: F=m(a). I learned how to apply the knowledge of the second law to determine mass and value of forces when an object is accelerating. When calculation the sum of the forces for an object that is accelerating just set the sum equal to ma instead of zero. I also learned about apparent weight and discovered that the apparent weight of a body is the force the body exerts on whatever it is resting on. Another thing I learned about is pulley systems and add wood machines. This is where there are two connected objects hung over a pulley, with one possibly resting on a table. I was able to create net force equations for these systems and then find the value of different variable. The final thing I learned about was the force of friction, I learned how to calculate friction and the coefficient of friction (expressed in mu). To solve for variables in these types of problems we used equations from both kinematics and dynamics.

What I have found difficult about what we have studied is the problems containing the coefficient of friction. In these problems you use equations from this unit and the last. Sometimes the answer is not apparent at first but when you keep substituting you are able to cancel out variables. I feel that as I get more practices with these types of problems I will be more comfortable solving them.

My problems solving skills are good in my opinion, and I feel that they have improved over this last unit. During this unit I have had to look at not just what we are learning currently but equations that we learned in the beginning of the year. I had much larger set of possibilities from which I had to choose the rights way to solve the problem. I think I have gotten better at doing this and I look foreword to more opportunities to hone my problem solving skills as the year progresses.

## Friday, January 8, 2010

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