Sunday, January 10, 2010

Newton's Second Law

This is what I learned about Newton's second law...

Newton's second law states that the acceleration of an object is directly proportional to the net force, and indirectly proportional to the mass of the object. When I first saw this, I have to admit that I was very confused. However when I was given the equation F=ma, I understood the concept. "F" is the variable for the sum of the forces, "m" stands for mass, and "a" stands for acceleration. This equation is the foundation for a=F/m. The second equation is used to find the acceleration of an object that is under contact of a force. Now I understand this law thoroughly. An easy way for me to think about it is if someone pushed a ball across the floor with an applied force, then the object would obviously accelerate if you think about it. Also, if you pushed it four times as hard, then the ball would accelerate four times as fast. This thought made the law very clear to me. During this unit, we also learned about apparent weight. Apparent weight is the amount of force an object exerts on the surface it is on, where as actual weight is the amount of gravitational force that acts on an object. Another thing we learned was about friction."The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it." There are two types of friction, kinetic and static. Kinetic friction occurs when an object is in motion, and static friction occurs when an object is at rest. We also learned about the coefficient of friction,mu. The equation is Ff=Fn*mu. We have learned a lot about this unit, and so far it has been filled with fun!

What I have found difficult about what I have studied is when to set the sum of the forces equal to ma. At first, I was very confused about this, but I later figured it out: the sum of the forces is set to ma if the axis that the motion is occurring in is being involved in the sum of the forces equation, and the sum of the forces is equal to zero if the axis where the motion is not occurring is involved in the sum of the forces equation. I also was a little confused about when to find the sum of all the forces and when to find the sum of only the forces in the axis of motion. These two things were the most confusing for me, but it didn't take me long to figure them out.

I believe that my problem solving skills have improved tremendously. I am very efficient now, and I am able to tell how I can figure out various unknown variables in problems. I am also very comfortable with the FBDs and the new equations. Overall, I believe that I have gained more confidence in being able to solve problems.


  1. Excellent posting! Your reflection is very thorough and I like that you also included a comment about apparent weight.

  2. your posting was very good, I don't think you missed anything. I like how you used the equations, its easier to understand.