Newton's Laws of Motion (the number one killers in America)

This unit my Honors Physics class learned about Newton's Laws of motion.

We began, naturally, at the very beginning with Newton's First Law of Motion, stating that "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," as quoted from our classwork book. This law predicts the behavior of both objects at rest and object that are moving around, or more basically stated that an object will just keep moving or sitting there unless an unbalanced force decides to mess with it. This is called inertia, the same law that makes you lurch forward when you hit the brakes on your car or throws you over the handlebars of your bike when you hit a rock. An unbalanced force happens when one force is greater than the other, and where this is unbalanced force we have net force, or the vector sum of all the forces action on one particular object. One important fact to know is that force is measured in Newtons. In order to understand forces you have to understand the difference between mass and weight. Weight is a force, therefore measured in Newtons, and is the Earth's gravitational pull on you, and mass is measured in Kilograms (in the SI units) and is what you would see on a common house-hold scale if you were to weigh yourself. Newton's First Law of Motion leads up to the knowledge of translational equilibrium. For the object to be in equilibrium, the net force has to be zero. After this long journey of understanding, we skipped over Newton's Second Law and right to the Third, tucking it away for later.

The Third Law simply states that if an object (the action force) exerts force on another (the reaction) , it will exert an equal force right back on it. For example, if I touch a desk and exert force on it, it is in turn touching my hand and exerting force on IT.

And finally, we learned about Newtons second law, which involves quite a bit of math. It states in our classwork book that "for a particular force, the acceleration of an object is proportional to the net force and inversely proportional to the mass of the object." That's a wordy way of saying that when you multiply the mass and the acceleration together, you make the sum of the forces. Remember that force is shown in Newtons. With this formula, you can find out the acceleration of a motion, the mass, and the net force, which is pretty awesome. You can also solve problems with friction and pulleys, because it all uses the same formula in it, but with friction there is another special friction equation that you have to work in those problems, too. And with all these laws, you can better understand forces and finding their value and why physics is why it is.


What I found difficult at times was, of course, the math. I will always struggle on the first try with math sometimes, but I get through it with the help of my friends and my fabulous father. By the end I have a pretty clear understanding of the equations and what to substitute for what and things like that. Another thing that tripped me up was the fact that these laws are mainly, well, standard rules. I can understand the rules, but the material they apply to change from problem to problem, and I have trouble connecting rule to problem sometimes, another thing I get help with.


When learning about forces, a problem solving skill I used was illustrations. Any FBDs/direction of motion arrows/vectors that I could draw, I drew. It helped me greatly as I am a visual person. Sometimes, when an illustration was given, I would draw information directly on that to aid me in drawing my FBDs and making connections. Also, writing down all my data and work, showing it step by step and keeping it neat, helped me not get frustrated or confused because I knew where all of my information was. One specific example was one of the many places in my homework where I wasn't careful and ended up getting frustrated and a lot of shouting went on between me and my dad because I claimed I was right and he knew I was wrong. My work, of course, was ALL over the place because I had been lazy and rushed. He told me to erase everything and I did, albeit reluctantly. When I rewrote my data and drew my pictures and wrote down the equation and solved for the variable and THEN plugged in the data, I finally could realized where I made my mistake because I wasn't trying to look several places at once and overlooking vital information. I used my problem solving skills wisely to help me conquer this unit.

Vectors and Projectile Motion

In this unit I learned about, of course, vectors and projectile motion. But what did I learn about them? First I learned all the equations needed to solve a projectile motion problem without an angle. I learned the equations to solve for time, distance, and velocity for both horizontal motion and vertical motion, as well as how to find the resultant velocity of a problem. I then learned how to apply these equations to problems involving projectile motion. Projectile motion at an angle was a little bit different. The acceleration is negative instead of positive, there's an angle that we have to deal with, and since we now have an initial vertical velocity, some of our equations have to take that into consideration. Along with projectile motion, we learned about vectors. Vectors are just the direction and magnitude of the object, so they were not that difficult to understand. Solving projectile motion problems with an angle aren't that much different from solving problems without, there are just a few more steps involved. I also learned how to add vectors. Adding vectors was one of the simpler things to do. All it is is finding the square root of Vx*2 plus Vy*2. The answer is called the resultant. The next step involves quite a bit of trigonometry. To find theta you multiply tan*-1 to the absolute value of Vy over Vx.

I found quite a few things difficult in this unit. First of all, since physics is all very new to me it takes me awhile to understand what exactly is going on. Once I do understand one problem, the next problem will have a slight twist that throws me off guard, then confuses me, then frustrates me. I usually spend a lot of time working on my homework or classwork with my dad, who understands this. Once I got the material, though, it was easier than I first thought it would be.

My problem-solving skills are a work in progress. Mrs. Gende, my physics teacher, gave us an organized plan to solving problems, which already helps me out a ton. I learn best with visuals, so in the more complex word problems I draw labeled diagrams of what is happening in the problem so that I can look at it and figure things out in relation to the picture. Sometimes I get lazy, and want to get a certain problem done faster than usual. The thing about physics though is that you have to be careful and take your time. With physics, if you rush you can make careless errors. Then I get frustrated and have to get my dad to help me. My dad teaches me lots of good study skills and easy ways to solve problems (he's the one who suggested drawing pictures for help) and writing down all the thoughts that pop into my head so that it's all on paper where I can see it, and it works.

There are lots of ways physics connects to everyday life. A huge example of this is sports, especially one where you have to kick the ball. If you know how far you're going to kick it, and you know how hard, then you can estimate at what angle you should kick the ball at. Launching a rocket is another example, because you deal with velocity, time, acceleration, distance, and angles. There are lots of things that you could apply projectile motion to in real life, with or without an angle. Projectile motion is a really important topic because of this, and learning it has shown a whole different view of everyday things, such as balls rolling off tables, bananas being launched at monkeys, and balls being kicked during a football game.