Newton's Laws of Motion

   Newton's laws have helped me understand the overall concepts of physics, and more specifically, motion, much better.  I have learned that:


Newton's 1st Law - Newton's first law states three basic ideas.
1.  An object that is not moving will not start to randomly move.  It stays at rest.
2.  If an object is moving, and there is not a constantly applied force, the object will continue to move at a constant speed.  However, if another force like friction is applied to the object, it will eventually slow down and come to a halt.  This is true in most cases.
3.  An object in motion will continue in the same direction unless acted upon by another force.  For example, if I am holding a rock in my hand and am moving my arm in big circles, whenever I decide to let go of the rock, it will continue to move in the direction that my arm and hand were last moving in.


Inertia is the resistance each object contains to not change it's state of motion at that moment in time.


I also now understand that the mass of an object is the same anywhere it goes, but the gravitational force (more commonly known as weight) can be different depending on where the object is in the universe.  For example, a 10 kg object is 10kg on earth, and on the moon, as well.  However, that same object will weigh 98 N on earth, but only 16 N on the moon.  This is because the gravitational pull on the earth is more than that on the moon.


I am now also very good at problems involving translational equilibrium, which is when the vector sum of forces upon one object add up to zero.  The object in translational equilibrium is not being moved in any direction because all of the forces cancel each other out.


Newton's 2nd Law - Newton's second law says that an object's acceleration is directly proportionate to the net force, and inversely proportional to the mass of that object.  For me, an example that helps me understand this law a lot better is if I am pushing a block across a horizontal table causing it to accelerate, and then proceed to push that block three times harder - the block will now accelerate three times faster.  The inversely proportional part of the law, using that same situation, means that if the block doubled in mass; the acceleration would consequently be half of the original acceleration.


Newton's 3rd Law - I have learned that Newton's third law basically means each action (or force) has an equal an opposite reaction.  For example, if I were to punch a wall: my fist would be exerting, for example, 800 N of applied force on the wall, and as a result, the wall would also be applying 800 N of force on my fist.  If we did not have this law, simple things like sitting down on a chair would be impossible.  The force of our body on the chair would not have a reaction force of the chair pushing up on our body, so we would simply fall through the chair.  


The last things I have learned are that apparent weight is the amount of force a body exerts on a surface it rests on, and mu helps find the amount of frictional force on an object, which is the opposing force of motion when an object is sliding, sitting still, or even rolling.


What I have found most difficult  in this unit is applying mu concepts to inclined planes.  On problem number 5 on homework 14, an object is sliding down a 30 degree angled ramp with no friction...I can not figure out how to find the mass, so in result I can't seem to find the acceleration, either.  I do not fully understand how to integrate vectors with aspects like friction on an object.  Also, I am sort of confused on what exactly mu is.  I don't really understand how it can have no units, and just be a number...What does the number represent?


I have studied mostly everything in this unit, but the concepts I have spent the most time on are pulley systems and how to approach problems involving a ramp (angle).  I have also spent a lot of time studying how to come up with equations and approach seemingly-difficult problems one step at a time.


My problem-solving skills have become much better due to studying this unit.  I think my ability to follow through each step of a difficult problem has gotten to the point where it comes way more naturally to me than it did before.  For example, I was working on homework #15, which talks about net forces and tensions, when I suddenly realized that everything I was doing, the steps I was taking, the equations, the relationships between the parts in the problem - everything was all very logical.    I think in the beginning of the year I struggled to understand the broad concepts and just focused on understanding the details; when now, I realize understanding what exactly you are doing and the general objective aids me much more than the small details when I go about solving a problem.  Still, I struggle most when first starting out an a problem.  It often takes me a while to think about what I am looking for, and make a plan in my head on how I will solve to get the final solution.


Overall, studying Newton's laws has been a very interesting unit and has greatly improved some of my key problem-solving skills.