In Unit 4, we learned about momentum. This unit was one of the more useful units, because I felt as though it completely related to real life. The equation for momentum is p=mass x velocity. An object will have a large momentum if its mass or velocity is large, or if they both are. Here's a useful video to help get a better understanding of momentum. Of course you can't expect the momentum of an object to always remain constant. It is going to change, and this change in momentum is called impulse. There are a couple of vital equations when dealing with impulse. They are, impulse (J) = force x change in time, and J= change in momentum (p). To increase the impulse, you must either increase the force, time, or both. However, when the impulse is constant, force and time on he equation are inversely proportional. Meaning that when you increase one the other decreases. There is one law that applies to momentum and it is the law of conservation of momentum. It states that the only way to change the momentum of an object is to exert an external force on it. No net force or net impulse equals no change in momentum. The official way to say this is that in the absence of an external force, the momentum of a system remains unchanged. As far as impulse goes, one thing to note is that the impulse of a bouncing is greater, because not only must the object be brought to a stop, but it must also be thrown back again. Here's a helpful video to help you get a better understanding.
Next up is collisions, which are actually pretty interesting. As we already know momentum is conserved in collisions (The net momentum before= the net momentum after). There are two types of collisions, which are elastic (two objects bounce of one another) and inelastic (two objects stick together). We can figure out the momentum that colliding objects have by using the first equation in elastic collision and the second in inelastic collisions.
(Remember m=mass and v=velocity; also m1, ma, m2, mb, v1,v2,va, and vb are all before the collision.)
Lastly, we have complex collisions, which involve to objects in different directions crashing together.
They create a combined momentum in a combined direction in inelastic collisions. A pool ball is a good example of a complex elastic collision. The cue ball hits the 8 ball at an angle and they both travel in different directions. However, in complex collisions momentum is still conserved.
This unit provided some difficulties when it cam to the lab problem. I had a hard time figuring out how to manipulate the equation in order to get the slope. But, it taught me a very valuable problem solving skill. It showed me that in order for scientists to prove their data sometimes you must manipulate the equation y=mx+b. This unit relates to real life situations, because it can help you learn how to minimize injury in crashes by increasing the time with things such as pads or airbags, in order to lower the force
GO PHYSICS!
In Unit 3 we learned about three major concepts. They are Newton's Third Law, Universal Gravitational Force, and tides. Throughout this unit my logic was challenged and things that I previously viewed as easy to understand were proved far more complex than I thought. First off I will start with describing Newton’s Third Law and how it is present everywhere in the real world. This law states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. So, this creates action-reaction pairs, which can be written as simple as, Dorian pushes on wall and wall pushes on Dorian. Anytime an object exerts force on another object, the other object will exert the same amount of force. Before unit 3, I believed that in order to win a game of tug-of-war one side must pull harder than the other. However, this is not true because no matter how hard one-team pulls the other team will pull with the same amount of force (Newton’s Third Law). To win a game of tug-of-war one team must use the ground as an outside force, so the team who pushes on the ground harder will win. Next up is The Universal Law of Gravity, which states that everything pulls on everything else in a way that involves only mass and distance. This law can be written as F=Gmass1xmass2/distance squared. The G in the equation is the universal gravitational constant, which equals 6.67x10 to the power of 11. When you double the distance you decrease the force by the one fourth, which is called the inverse squared law. The equation always follows this pattern. When someone thinks of tides they usually think that tides are caused by the moon’s force on the Earth. This is partly true, but the actual cause of tides is the difference in force on each side of the Earth. This is caused by the difference in distances form the moon that each side of the earth has. Thus, creating a tidal bulge that has a high tide on opposite sides and low tide on opposite sides.In this diagram A and C are experiencing high tides and the other sides are experiencing low tides. Also, the vector arrows show the difference in force from side C to side A.
There are two specific types of tides that we learned about. The first is spring tides, which occur when the moon, earth, and sun are aligned creating a full or new moon. At this time the high tides are higher than usual and the low tides are lower than usual. The next is neap tides, which occur when the sun is at a ninety-degree angle to the earth, creating lower than usual high tides and higher than usual low tides.
It is very difficult, at first to fully understand the fact that no matter how hard you push on an object that object will push back on you with the same amount of force. This totally goes against what I perceived as logical. This unit actually helped me improve my math skills, because while using the Universal Gravitational Law. Not being able to use a calculator taught me how to solve equations with exponents in a much simpler way than I had previously been doing. With the knowledge I have gained from this unit, I will be able to go to the beach and try to predict what tide is about to happen and whether it will be higher or lower than usual.
Unit 2 was a unit that presented may contradictions to the way i previously viewed falling objects and projectiles. The main overlying theme of this unit is Newton's Second Law, which is acceleration=net force/mass. The unit started of talking about free falling objects, or objects falling by the force of gravity alone with no air resistance. It is important to remember that a free falling object must start from rest and when an object is in free fall the force of gravity (which is 10 or 9.8 to be more specific) is its acceleration. Two equations can be associated with free fall and they are the distance or how far equation (distance=(1/2)gravityxtime squared) and the velocity or how fast equation (velocity=gravityxtime). Next we moved on to objects falling with are resistance. These objects have to things they must take into account, the force of the air and the force on the falling object. Instead of always being a constant acceleration, like in free fall the accelerations vary. We can find the acceleration by using the formula acceleration=Fweight - Fair/mass. Also, there is something called terminal velocity, where the Fweight and Fair are equal, the velocity stays constant, and there is no acceleration. So what happens when you throw an object upward? It must come down right? So we use the same equations we have for free falling objects to help us calculate the distance and velocity of the object as it rises. Remember that on this case the acceleration of the object will be negative ten meters per second squared. Lastly, we learned about projectiles, which is basically an object being launched at an angle. We must take into account the vertical and horizontal velocity in this situation, so the velocity of the object will never reach zero (unless it hits the ground). Horizontal velocity remains constant, while vertical velocity uses the sam principles as a free falling object, so the same equations can be applied. One thing that was difficult for me to understand is how to find the distance an object that has been thrown up travels. Because, I knew you could not use the distance formula due to the fact that it did not begin at rest. Eventually, I was able to grasp the concept that an object going up must come down and when it falls down it starts from rest. So, you must calculate that distance and it will be equal to the distance the object traveled up. Some of the projectile problems require a lot of problem solving skills. With the horizontal and vertical velocities, it makes it possible to apply pathagorean's theory. However, I believe I did very well in my problem solving and seemed to always come up with an answer at least. Everytime you drop something or something falls off of your desk these principles are being used and since I have a better understanding of them I know exactly what's going on. Also, when you shoot a basketball it is a projectile. Maybe, I can calculate the proper velocity and distance to shoot it with in order to make the shot everytime.
Unit 1 was a very intriguing unit, we started off with Newtons 1st Law, which covers the idea of inertia, or the tendency of things to resist changes in motion. Newton said that an object in motion or at rest will remain in that state unless acted on by an outside force. This force in its most simple form could just be a push or pull. Force can be gravitational, electrical, magnetic, or simply a muscular effort. So, you're probably wondering what its called when more than one force acts upon an object? Or maybe not, but it is called the net force. When an object is at rest or moving at a constant speed it has a net force of zero which means that the object is at EQUILIBRIUM. Once we understood these concepts we moved on to learning what exactly is going on when something is in motion. Well, there are a few things that one can take into account, like the distance an object traveled and how long it took it to get there (this = speed or distance/time), the direction something is moving and the speed at which it is moving (velocity), or the accleleration of an object (change in velocity). Acceleration is found by the equation a = change in velocity/ time interval. Once you find the acceleration you can plug it into the how far and how fast equations. The how fast equation helps you find what velocity something has by using the acceleration and time (the equation is, v=at). Lastly, the how far equation uses acceleration and time to find the distance in meters that an object traveled [the equation is, d=1/2a(t squared)]. This unit had some things that were fairly hard to get a complete grasp on. Such as, the fact that when something has decreasing acceleration, the object will still be increasing in speed. Because, normally when someone thinks of acceleration they think of speed, so one assumes that because the acceleration decreases the speed decreases. But that is just not the case. I believe that this unit has helped my problem solving skills. It has taught me that even when you don't exactly know the answer you must take your time and think about it in order to understand it. Try to figure out what exactly it's talking about, and what is the most efficient way to reach the answer. Physics has a lot of conceptual aspects, so you really must learn to think things through when answering questions. One connection I have made is between physics and precalculus. When you roll a ball at a constant velocity each interval of time, let's say each half second, the distance between where the ball was and where it is when you record the time goes up by the same amount each time. Meaning that this can be represented by a linear equation, and can be graphed by using a scatter plot. This means, I'm learning physics and precalculus at the same time!
This upcoming year in physics I would like to learn the main principles of physics and exactly what physics is all about. Coming into this class I pretty much have no idea what to expect or even what i'm going to be learning about, but I hope by the end of the course I will have a solid undertstanding of the concepts we will be learning. Physics has a lot of real world implications, I mean basically everything has some sort of physics applied to it. That is why I think it is very important to learn about physics, because it helps one get a better understanding of the things going on around them. Coming into physics this year the only questions I have are what exactly are we going to be studying and does are we going to be doing many projects throughout the course of the year? Some of the goals I have for physics this year are to most importantly recieve good grades, but to also make sure I have a complete grasp of the information taught during this course.
