Physics Semester 1 Review

Uugh, I can't believe that the first semester is already over and that it's only been three weeks. It feels as though we have spent months in this class and yet hardly any time at all. That's probably because we learned so much these past three weeks.

In Unit 1, we learned about accuracy and precision, conversions/stoichiometry, scientific notation, and the different types of graphs. We mostly focused on the graphs and the different relationships their variables have with each other, which was helpful, since we're still using that knowledge now while making graphs.

In Unit 2, we began learning about kinematics. We learned about motion maps and how to draw them, and about scalar and vector quantities. We also learned about the difference between distance and displacement, speed and velocity, what acceleration is, as well as about the three graphing rules.

In Unit 3, we learned more about acceleration. We learned how to draw Distance vs. Time graphs, Velocity vs. Time graphs, Acceleration vs. Time graphs, as well as how one graph could help us draw another one. We also learned about the DAT, VAT, and VAD equations and how to use them, as well as what steps to take while solving the equations.

In Unit 4, we learned about projectiles. We learned about how to draw diagrams of projectiles and how to draw graphs. We also learned that when making graphs, the two axes are independent. We also learned how to use the DAT, VAT, and VAD equations to find whatever factors we needed. These problems were complicated at first, but became a lot easier with practice.

In Unit 5, we learned all about forces in equilibrium and how to use vectors. We learned the bureku technique, which allows us to break up diagonals on free body diagrams in order to find the information we need. We also learned what force is, which is a push or pull and is a vector quantity, as well as a couple types of force. Lastly, we learned Newton's three laws of physics, which provide us with a greater understanding of why things act the way they do.

In Unit 6, we focused on Newton's second law, which states that Fnet=ma. We learned how to draw and do problems that involve acceleration, which we didn't know how to do in the previous lesson. We also learned more about friction, and how there are two different types: static and kinetic. Static friction is stationary motion, while kinetic friction is moving friction. We also learned how to find the force of friction, which is equal to the coefficient of friction times the normal force. The coefficient of friction is pretty much based on the stickiness of the object.


In all honesty, I absolutely love this class! Mr. Blake makes learning interesting by adding in jokes and relating to us, unlike other teachers, who would just talk at us without waiting to see if we understand. I think the pace of this class is almost perfect, if not a little fast sometimes, but I don't really think there's any way that can be fixed, since we have so much to cover in so little time. I also like how I am beginning to look at things outside of class and being able to relate what they are doing to what we are learning in physics.

Most of the stuff we learned I understand decently, but units 5 and 6 are definitely the two units that I struggled the most with. I have a hard time doing the bureku technique as well as drawing free body diagrams, since I find them so confusing. However, the reason that I have such a hard time with units 5 and 6 could just be because we only learned them this week, and we didn't have enough time to practice. Either way, I'm really looking forward to another fun 3 weeks of physics!!

Physics Unit 6

Today we started learning about how to find the acceleration of objects by using Newton's Second  Law of Physics, which states that the net force of an object equals its mass times its acceleration (Fnet=ma). This whole new system is both terrifying and confusing for me, but I hope that this post acts as a good review for me, and hopefully by looking over my notes again, I gain a stronger understanding.

So, there are three steps to take: 1) draw free body diagrams, 2) find acceleration of the system, and 3) choose one mass to find T. Using these three steps, I will show an example problem to help clarify what you are supposed to do.

Problem: There is a box of 50 kg on top of a frictionless table being pulled by a piece of rope which is in a pulley (changes direction of force). At the end of the rope is another box hanging over the side of the table with a mass of 10kg. Find the acceleration of the system and its tension of the string.

1. Draw free body diagrams.

2. Find acceleration of the system.
Ok, so for a while I didn't understand how to find the Fnet, and I'm not entirely sure if what I think is correct actually is correct, but oh well. The way I think you're supposed to find the Fnet is entirely based on your free body diagram. With it, you can see what forces you can use and which you can't. The normal force and the weight of the 50kg box are equal, which means that they have a difference of zero newtons. The 10kg box, on the other hand, has a much higher weight than it does tension, since the box is accelerating down. This means that when pluggin in the answers for the Fnet, you would subtract the smaller value from the bigger one, in this case that would mean that the tension is being subtracted from the weight of the 10kg box. Since the 50kg box is connected to the same string as the 10kg box, they have the same amount of tension, which would be added to the Fnet, since the variables are on the same axis. As for the rest of the equation, you can just plug everything in based on the information you already know.

3. Choose one mass to find the tension.
Once you find the acceleration, you use the same Fnet=ma equation to find the tension. You only had to choose one of the two boxes to find the tension, but I wanted to show that the tensions were the same, so I solved for both. Anyway, for the 50kg box, like I said earlier, its normal force and weight are equal, so the only Fnet I had for it was its tension. The 10kg box, however, had its weight and tension, so I used both. Once you figure out what exactly to plug in, the actual solving of the equation is relatively simple.



I'm not entirely sure if I was even right about my explanations on how to solve everything, but on the bright side, at least I now have a somewhat stronger understanding of how to solve problems like these.

Physics Unit 5 (Part 2)

In class today, we learned about Newton's last two laws of physics, so I thought that I would spend this whole post just going over what each law means and how it applies to every day life.


The first law is the Law of Inertia, which states that an object in motion tends to stay in motion while an object at rest tends to stay in rest unless an outside, unbalanced force acts upon it.

The picture above shows Caitlin and me in Driver's Ed, which is a three hour class we attend on Mondays and Wednesdays after physics, and as you can see, we are enjoying every minute of it.  In terms of Newton's first law, Caitlin and I are the objects at rest. We basically sit in the exact same spot hours at a time doing pretty much nothing. In Driver's Ed you eventually give up staring at the clock and sink deeper and deeper into a haze of tiredness and road signs. By the time you are two hours into Driver's Ed, all you can do is fight to stay conscious, so when the instructor announces that it's time to go on break, you are so unprepared for the news that you are instantly overwhelmed with the feeling of elation. Said elation, in relation (it rhymes!!) to the Law of Inertia, is the unbalanced force that pushes the object at rest into motion, and is what causes Caitlin and me to move out of our states of rest and practically skip out of the classroom to do a celebratory dance. 

Newton's second law is the Law of Acceleration, which states that the acceleration of an object is directly proportional to an object's net force, and the acceleration of an object is also inversely proportional to the object's net mass. The equation for the law is Acceleration = Sum of force ÷ mass. 

In this picture we see our friend, Bob, who likes golf. Newton's second law talks about how acceleration is equal to the amount of force of an object divided by its mass. Bob just hit a golf ball, and it has a high acceleration.

Now, in this picture we see Bob, trying to hit a truck out of the way because it is right above his golf ball. Unfortunately, our friend Bob isn't all that smart, and he thinks that he would be able to move the truck if he hits it with his golf club. Bob had swung with all his strength when hitting the golf ball, and since it went so far, he thinks that if he hits it just as hard, the truck will move. Too bad Bob didn't know about Newton's second law of physics. Because the mass of the truck is so much greater than the mass of the golf ball, the acceleration of the truck is going to be a lot less than the golf ball's. In other words, the truck isn't going to move at all.



Newton's last law of physics is the Action-Reaction law, which states that for every force (action), there is an equal and opposite force (reaction), which is equal in magnitude, but opposite in direction.

In this picture, my friend's and I are playing a game at Dave and Buster's that involves pushing the buttons that light up in order to get more points. My friends and I are very aggressive, so we ended up hitting the buttons incredibly hard, which in turn, made our hands incredibly sore after. Part of the reason why our hands were so sore, besides the fact that we were just slapping hard plastic over and over again, is because of what Newton's law stated. As we were hitting the buttons, the buttons were pushing back against our hands with the same amount of force that we were hitting them with. In other words, the whole time we were slapping the buttons with all our strength, the buttons were punching us back just as hard. It's funny, because right now the "I am rubber, you are glue; whatever you say bounces off me and sticks onto you" saying is going through my head right now, and it actually applies to Newton's law in a way, except instead of saying something we're just hitting the rubber and the rubber's just hitting us right back.

Physics Unit 5

Today, we started Unit 5, which revolves around forces in equilibrium. Force is either a push or pull and is a vector quantity. Force in equilibrium is when the force is balanced. We learned about different kinds of forces as well as the Newton's first law of physics, which has to do with inertia; it states that an object in motion will stay unless acted upon by an outside, unbalanced force. Inertia, by the way, is an object's ability to continue doing what they are doing.

We reviewed vectors and how to solve them (woohoo, trigonometry). We learned that vectors would be equivalent if they have the same magnitude and the same direction. Basically, if two vectors start at the same spot and end at the same spot, they're equivalent. While there are diagonal vectors, we only focused on how to make vectors into right triangles by drawing extra vectors, in order to make it easier to solve with vectors. By having the vectors as right triangles, we can use SOH CAH TOA to find the lengths of vectors or their angles.

We also learned the three steps to using vectors to solve for sides or angles, which is:

1. Break up diagonals (Bureku) into x and y.

2. Add all values together to get a sum (axes are still independent) resultant.

3. UKERUB (Bureku backwards) - take x and y sums and create a new vector.

Physics Unit 4 (Part 2)

In the beginning of class, we had our lab practical, which was basically the same thing that we did in the previous class, where we launched a plastic ball out of a ball-shooter-thing. The reason for shooting the lab/lab practical was to practice our equation solving of two separate variables, which we did in order to predict where the ball would land.  During the lab, we kinda failed a little bit, and we were consistently hitting the same area in between the 2 and 3 section of the paper (yay precision!). HOWEVER, during the lab practical, we consistently hit right around the middle of 5 (yay accuracy AND precision!!) and it was kind of amazing (my group cheered really loudly and I felt really bad afterwards for doing so). If you squint and move your face about an inch away from the computer screen, you can see the little dent that we made and circled with a pencil for better evidence. 

After the lab practical, we basically spent the rest of the day learning about how to launch rockets while predicting various elements like where they would land, or what their velocity would be. We used SOH  CAH TOA, with the original velocity as the hypotenuse, the horizontal initial velocity as the adjacent, and the the initial velocity of y as the opposite. We only used one angle for solving equations to keep everything consistent. For example, if you had an initial velocity of 25 m/s, and the angle was 40 degrees, and you wanted to find the initial horizontal velocity, you would do Cos 40° = VoX ÷ 22 m/s, you would find that the initial horizontal velocity would be 19.2 m/s.

Physics Unit 4

So, we started Unit 4 today, and we started off with learning how to use the DAT, VAT, and VAD graphs on objects that are moving both up or down and left and right. In other words, we are learning how to use the equations on stuff that is either being thrown or dropped. The idea of graphing two different things at once was a really terrifying idea for me, but now, while it is still very terrifying, using the equations on them isn't as difficult as I thought it would be.

We had a lab today which involved shooting a little plastic ball out of the object in the picture above. The reason for this lab was to practice solving for the two equations on both distance and height, since the ball was moving forward and down at the same time. This lab along with all the other practice problems that we had were really helpful and I gained a stronger understanding of what to do. Unfortunately, while my group's lab practice wasn't very accurate, we were very precise and hit the same area every time we tried shooting the ball.

Physics Quarter 1 Summary

I can't believe we're already done with the first quarter! Time sure flies when you're having fun, doesn't it? Well, you know, it's either that, or time just flies by when you're taking Physics over summer and learn a week's worth of information a day... but I'm pretty sure it's just 'cause we're having so much fun.  *cough* Anyway, we learned a lot in the three units we went over.

Unit 1
One of the first things we learned about was that the variables on a graph had specific relationships with each other and that they had special equations to linearize them. We also went over how to use scientific notation, which is basically where you take a long number like 123,000 and write it as a decimal being multiplied by the appropriate power of 10, which would be 1.23 x 10^5. This came in handy when solving equations, since it allows you to write long numbers in a shortened and simpler way. We also went over stoichiometry, which is when you convert a unit into a different unit (ex. grams to kilograms). Lastly, we relearned the differences between accuracy and precision.

 

Accuracy is when you are close the a certain value. The picture on the left demonstrates accuracy, because the darts are all close to the bullseye, which is what you normally want to hit when playing darts. Precision is when you are consistently hitting the same value, which is demonstrated in the picture on the right. As you can see, while the darts aren't hitting the bullseye, they are all landing in the same area on the dartboard, which is precision.

Unit 2
In Unit 2, we learned all about how to make graphs and the rules of graphing, which are:
1. The slope of a position vs. time graph is the velocity.
2. The slope of a velocity vs. time graph is the acceleration.
3. The area under the curve of a velocity vs. time graph is the distance travelled.
We also learned about the scalar quantities and vector quantities. A scalar quantity is a measurement that has magnitude, while a vector quantity is not only a measurement that has magnitude, but direction as well. Two vector quantities that we learned about also are velocity and displacement. Velocity, is speed with direction, and is based on displacement and a unit of time. Displacement, is your change in position. Below is a picture of a problem involving displacement that we did in class, which is a lot better description than I would've been able to make.

Unit 3

We learned a lot about kinematics equations and the steps you have to follow while doing them. The equations are d=1/2at^2+Vot (DAT), V=Vo+at (VAT), and V^2=Vo^2+2ad (VAD). These equations are useful when trying to find one of the variables that a question asks for. For instance, if you are given the distance, acceleration, and initial velocity, and you are trying to find the amount of time, you would use the DAT equation. The steps that you have to follow when solving with these equations are:

1. Write down the question

2. Write down the givens

3. Sketch a picture of the problem

4. Choose an appropriate equation

5. Plug and Chug (plug in the answers and solve)

6. Box the answer

7. Check to make sure your answer makes sense

Physics Unit 3 (Part 2)

 

Today, one of the things we focused on the most was acceleration. The picture above shows the main example we used in class, which was whether or not two objects of different sizes would fall at the same rate and hit the floor at the same time. We tested this by dropping two balls (hehe), a four-square ball and a tennis ball, at the same time. While they obviously have different masses and different volumes, they still hit the floor at almost the exact same time, which proved to us that Galileo's theory on gravity was correct. However, if you drop a piece of paper at the same time you drop a rock, they will not land on the floor at the same time because of something called air-resistance. 

We also learned about how an object's velocity would change when thrown up into the air. We learned that it would be fastest as soon as it left your hand, and that it would gradually lose its velocity until it reaches its very highest point, in which case it will be 0 m/s. Once the object starts falling back down, it will gradually pick up speed, and if you were to catch the object at the same height that you threw it, its velocity will be the opposite of what it was when you threw it.

Physics Unit 3

Picture of my brother's skateboard

Today, we conducted an experiment where people rode a skateboard and the "danger board" down a slanted surface. We measured their times in 5 meter intervals, in order to collect data on how fast they were going. When graphing the data, we saw that as the distance of the skateboarder and the amount of time increased, so did their speed. In other words, they accelerated.  Through this experiment, we gained a greater understanding of the rule that curved slopes of Distance vs. Time graphs give you the acceleration of the object. 

We also learned a few equations that can help us find distance, acceleration, velocity, etc. as long as we have all the other variables that need to be plugged in. These equations are:

d= 1/2at^2 + Vot (d, a, t)

V= Vo + at (v, a, t)

V^2 = Vo^2 + 2ad (v, a, d)

We also learned the steps to answering problems so that we'll be able to have a better understanding of what we are supposed to be finding and what we have to do to find it. The steps are:

1. Write down the problem

2. Write down what's given

3. Draw a sketch

4. Choose an equation

5. Plug and Chug

6. Box Answer

7. Check to see if it makes sense

Physics Unit 2 (Part 2)

Today, we learned about acceleration, which is the change in velocity per unit of time. Velocity, in case you may have forgotten, is speed with direction. The picture above is an image of me in a go-kart race (which was incredibly stressful). The main goal of go-karting, when I went, wasn't so much to beat everyone else and finish the race first, but rather to go as fast as you can and challenge yourself. This means that you have to try and go as fast as you possibly can, which is all fun until you have to go around a corner and you end up spinning into the border. The only way you can go around a bend while still going as fast as possible, is to slow down in order to go around as smoothly as you could. When you are going slower, your velocity goes down, since you are going a shorter distance in a shorter amount of time; in other words, you are accelerating.

We also used the nifty little tool in the picture above in our labs today to learn more about how Position vs. Time graphs work, which then lead us to understanding more about Velocity vs. Time graphs. The labs in general were really helpful for me, and I was able to gain a stronger understanding of how to draw Velocity vs. Time graphs, as well as how to find the distance travelled by using said graphs. 

Physics Unit 2

This is a picture of my friends going down the stairs of a hotel we were staying at during our trip abroad in Japan. This picture relates to physics, because in unit 2 we are going over kinematics, which is the study of motion. The first thing we learned about in unit 2 was how all motion is relative. We learned that even though you are sitting in place, while you are not in motion relative to the room you are in, you are in motion relative to space, since the earth is constantly moving. Another example would be of my friends in the picture above. They are going down the stairs together, and since they are going at the same speed, they are not in motion relative to each other. They are, however, in motion relative to the floor.

We also learned about scalars and vectors in this unit. A scalar quantity is a measurement that has magnitude, or muchness, while a vector quantity has not only magnitude, but also direction. An example of a scalar quantity would be that we walked down 10 feet of stairs, while an example of a vector quantity would be that we walked down 10 feet of stairs to the lobby. We also learned about the differences between distance and displacement, and how distance is scalar while displacement is vector.    Distance, as you already know, is just the length of a route that you take, and displacement is the change in position that you have ater moving somewhere. An example of displacement while using the same scenario of the trip abroad would be going down the stairs from our room to a restaurant, eating, and then going back up to our room. Our displacement would be zero, because even though we had moved, our going back to where we started meant that we hadn't actually changed our positions.

Physics Unit 1

In the beginning of Unit 1, we (re)learned about the differences between precision and accuracy. When going on the dictionary to look for the definitions of both words, their definitions had the opposite words in them, which didn't provide a very clear definition of what they meant. However, while they have a similar meaning, they have two aspects that separate one word from the other.
Accuracy is being close to a certain value, while precision is being close to a value consistently. To make things more understandable, look at the two pictures of the (badly drawn) dartboards. The main goal of playing darts is to hit the bullseye and get the most points, so if you are hitting the bullseye and the areas close around it, that is accuracy, because you are close to the target that you wanted. Precision, on the other hand, would be if you not necessarily hit the bullseye every time, but one area consistently.

Another big part of Unit 1 were the Pendulum Labs. Through them, we were able to categorize the relationships of the independent and dependent variables in the experiments using the graphs that we had learned about on the first day of class. I found that the labs helped a lot to show me how they actually did relate to what happened in real life, rather than them just being confusing graphs/math equations that I had to memorize.
(I didn't have any pictures of pendulums or the graphs, so I took this picture from the homepage... sorry)

Introduction to Me

My name is Joy, my friends are all dorks, and I fit in among them as a fellow dork. I spend all my time watching TV shows, movies, and going on Tumblr. I have taken Biology over the summer going into freshman year and Chemistry in sophomore year. I kind of hated Geometry, and I'm going to be taking Alg. 2/Trig. next year. In chemistry I began to apply concepts we learned into my life, and I hope to gain a similar understanding in physics, where I will be able to understand why things happen the way they do.  The "story" behind the picture that I'm using is that Caitlin and I are not only taking Physics together but also Driver's Ed on Mondays and Wednesdays, so we had an hour together to do homework and eat lunch. The reason I'm making a funny face with her is because I hate taking nice pictures of myself because I look weird, so I always try to make funny faces so that I never unintentionally look weird in pictures.