Thursday, December 9, 2010

Newton's Amazing Laws of Motion

This is what I learned about Newton’s Laws of Motion. In this unit, we learned about Newton’s Laws of motion and how to find the different forces of the scenarios we were given.  Newton’s First Law states “An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.” This was the easiest law to understand. All it says is things will keep doing what they have been doing unless an outside force acts upon it. The word for this is Inertia. Inertia is the resistance an object has to change its state of motion whether it is stationary or in motion. In Newton’s first law we learned about equilibrium and net force. Net force is the sum of all the different forces acted on the object. An object is in equilibrium when the net force is equal to zero. Equilibrium is only used when an object is at rest or is traveling at a constant velocity in a straight line.
Newton’s Second Law of Motion 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. The direction of the force is the same as that of the acceleration." Basically meaning the acceleration of any given object is reliant upon the net force and the mass and that the direction of the force on the FBD(free body diagram) is the same direction as the acceleration. The equation we used to find acceleration(a) was a=ΣF/m. This also was fairly simple. All you have to do to find any of the given forces, you just need to tweak the equation and viola! You can now find ΣF using the equation ΣF=ma. Newton's Second Law also deals with apparent weight and pulley systems. I understand apparent weight much better now. There is a difference between a body's actual weight and apparent weight. Actual weight is the amount of gravitational force acting upon the body. Apparent weight is the reading of the scale in different situations. If a body is moving at a constant acceleration or not at all, the apparent weight is equal to the actual weight. If, however, a body is accelerating upwards, the apparent weight will be larger than actual weight, if accelerating downwards, it will be less than the actual weight, and if in free fall, it will be zero because the body will have lost contact with the scale. Pulley Systems proved most difficult to understand. When working with pulley systems, more than one FBD is required, and also you need to only use the forces acting in the direction of motion. From there you write out the ΣF equation and solve for the unknown.

Newton’s Third Law states “when one object exerts a force on another object the second object exerts on the first an equal force in opposite direction” which basically means everything has an action and a reaction force. So if you were driving along the freeway and a bug hit your window, according to Newton's third law, the bug hit your window, but your window also hit the bug.

 What I have found difficult about what I have studied is problems when we are missing more than one piece of information. Like when the mass is not given and you are looking for the applied force which you cannot get without the mass. How get past the fact that the mass is not given is: you keep the variable and eventually the variable will be canceled out. Like if you have 128m=14mFa you can divide by 14m and get Fa= 9.14N. My problem solving skills increased the more problems I worked. At first I usually do not completely understand the material, but once I work a couple of problems in the classwork, the material begins to make more sense to me. I have tons of “light bulb” moments where all of a sudden everything makes sense.  My areas of strength are finding the mass and weight of objects, and apparent weight. One of my weaker points is pulley systems and equilibrium. Pulley systems confused me mostly because I missed the lecture in class on them and had to teach it to myself. In pulley systems there is more than one FBD and therefore more forces and more masses that I need to work with. Overall this unit has been pretty easy to grasp and I definately understand physics better for it!

My Tagxedo of Amazing Physics Terms!


  1. Excellent reflection, you covered everything in depth and you explanations are very clear.
    Please remember to add your Tagxedo!
    Great job!

  2. Really well-written reflection, nicolaaa. Like dgende said, add your Tagxedo. You may want to consider providing the definitions for an action force and a reaction force. Just a tip: re-read your entire blog aloud, that way you can search for your own typos.

  3. Alrighty! Thanks Sabeeh and Mrs. Gende!! I added my tagxedo, sorry bout that! Haha..