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About this blog

My AP Physics C blog that I wish had a better title. Here goes...

Entries in this blog

 

Laundry Mishap

About a week ago, I walked down into the basement to check on my laundry only to find a large puddle of water on the floor. We had temporarily fixed the pump that brings the water from the basement up into the septic but it seemed to have broken again. We need pumps for appliances below our septic tanks because the water does not have the ability to move from low to high (high being the location of the septic tank; low, my basement) without an external system doing work on it. Because of gravity's natural pull downwards, water wants to go down. To go up the pump must create power to do the correct amount of work to push the water up into the septic. Without it, the water overflows the location of the pump and floods the basement. 

kateh516

kateh516

 

An Octopus' Garden

The title of this blog post is pretty irrelevant except for the fact that I will be talking about an octopus. The said octopus was won by a friend of mine for selling a bunch of a certain item for a class fundraiser (good job making those sales- woot woot!). The octopus was one of the gel forms that sticks pretty much anywhere. We threw it against the wall cabinet in the physics classroom and watched it stick for a short amount of time before it started to slide down. For a brief period of time the coefficient of static friction was great enough to hold it up against the force of gravity. Once it started to move and the coefficient was now kinetic (because things in motion are kinetic) it had a little bit of grip left to it but it continued to slide down until it dropped completely. 

kateh516

kateh516

 

Air Bags

Once upon a time, air bags were nonexistent. Now they are a standard feature in all new cars. This became a requirement for cars in 1998. When you get an accident at a high speed where the vehicle stops quickly, we know that the person inside wants to keep moving in the same direction at the same velocity as before the crash. Seat belts help to prevent the body from slamming into the wheel or flying out through the windshield. Your head can still fling forwards. The air bag deploys in order to slow the person over a longer period of time. It "catches" the head (or body) and brings it down to a slower speed over a greater period of time so the overall impulse (impulse= force*change in time) is much smaller. A higher impulse force on an important part of the body, like the head, causes injury or even death. 

kateh516

kateh516

 

Dog and Cat Wars

I own two wonderful pets, a dog, Henry, and a cat, Willow. Let's just say they... tolerate each other. As my dog has gotten in to his elder years (He will be 11 this August), chasing the cat (she's turning 5 in June) has become less interesting to him. I've noticed on the days he does decide it's worth it to get up and run after her, she is able to turn the corner a lot faster than he is. I figured this must be because of her lower center of mass. She can turn at a lot higher speed without her legs flying out from under her. My dog, on the other hand, takes longer to turn since he is much bigger than Willow. His age and his lack of control of his left hind leg due to an injury earlier in life also could contribute to his inability to catch up with her. 

kateh516

kateh516

 

Remember Scooters?

In Orchestra today, two kids rode past our room on their scooters. After discussing why two 8th graders were getting to school late, we started reminiscing about the scooter days. Remember those Razor scooters that hurt so much when they accidentally swung into your ankles? Yeah, those scooters. So I was one of the fortunate kids to have a scooter and one memory I have of it is the day I learned you must avoid, at all costs, scootering barefoot. Oh yes, bare feet and scooters are not a good combination. I remember wheeling around my driveway and then needing to slow down to turn and head back. I stepped on the brake and all of a sudden my foot got very, very hot. I asked my parents why and they told me that brakes make things hot because of the friction it creates. Now that I'm older, I understand why this heat is created. When you step on the brakes, the friction between the metal and the wheel is increased greatly. Brakes work to bring the kinetic energy to a lower value (reduce the speed). To do so, some energy must be released. This energy is released in the form of heat which I felt on the bottoms of my feet through the metal brake at the back. So, next time you go out and scooter (don't lie to yourself... you know you want to bring that dusty scooter in the corner of the garage back out) think of the physics and enjoy scootering at a whole new level!

kateh516

kateh516

 

Breaking CDs

A YouTube channel I enjoy to watch is that of The Slow Mo Guys. For those of you who aren't familiar with them, they film many different things- paint on speakers playing music, a bullet being shot through a pool of water, etc.- with high speed cameras that capture millions of frames per second. In one video, they spin a CD at 23,000 rpm (the critical spin rate of a CD)  at which it begins to shatter due to the extreme forces it feels at this high rpm. They catch all of this in slow motion making it an interesting (and physicsy) watch! I've included it below. Enjoy!  

kateh516

kateh516

 

Popping Popcorn

Popcorn is a tasty snack that has existed for many centuries. The other day I was wondering how exactly it worked and figured there must be some physics behind it. After experiencing pressure created by the temperatures it is put under, the hull of the kernel splits and turns inside out. The water vapor that is released makes the popping noise. If you have ever made popcorn in a pot you will have seen that popcorn "jumps" in the air. I figured that the release of the water vapor directs a force against the bottom of the pan. As we know, for every force there is an equal and opposite force. The force released from inside the kernel points down towards the pan and then a force is exerted back in the opposite direction on the kernel causing it to "jump" up into the air. What a great physics snack!

kateh516

kateh516

 

Half Chaps

In the English style of riding, sometimes you may notice a rider wearing extra material around their calves. These are known as half chaps (I've included a picture below for better reference). Riders may choose to wear half chaps as a way get a better "feel" of the horse and keep your leg in the proper position. The coefficient of friction is increased by riding with half chaps as most have a grippy (for lack of a better term) fabric on at least the inside of your calf. The coefficient of friction is much greater using chaps than it would be wearing jeans, breeches or any other pant. When riding the goal is to keep your shoulders, hip and heel all in a straight line from top to bottom. Half chaps aid in lessening the movement in your calves as you ride, which allows you to keep the straight line from shoulders to heel. 

kateh516

kateh516

 

Tire Swings

On Easter, I had the pleasure of celebrating with a friends family (because all of my family lives in a land far, far away). Her cousins really liked playing on the tire swing they have in their yard. I don't blame them, tire swings are pretty swanky. For some reason they really liked when I pushed them. Maybe it was just because I was a new person that isn't family. Or, maybe it's because of physics. My friend and I, being the oldest kids there, ended up supervising after we ate Easter lunch. When my friend pushed them, they seemed to enjoy it but they really did when I pushed them. That's all because of potential energy and it's transformation into kinetic energy. Being 6'2" (an entire foot taller than my friend) I was able to pull them to a much higher height before letting them go. This means they had a larger potential energy as P=mgh. The height they could reach with me pulling them was much larger. Due to the conservation of energy the kinetic energy would also be much greater with me pulling them allowing to reach a larger velocity, K= .5mv^2. And when you're little, faster means more fun. 

kateh516

kateh516

 

Hiking is Phun!

I would like to start off by apologizing for the title. Sometimes I try to be punny and I should know by now I'm really bad at it.  Anyways... I was on spring break this week and a group of my friends (they're some really cool people) took a day trip where we found a pretty gnarly place to take a hike. It was a pretty awesome adventure and with any adventure, there has to be physics involved. We all hiked to the top of trail but, did we all do the same work? No! Why you ask? Because work is equal to the force*displacement. We all were displaced the same amount (since we all started from the bottom and hiked to the top) but since force is equal to mass*acceleration this number would vary. We all walked up at about the same pace but we probably aren't all the same mass (I did not weigh everyone who went on the hike so if we all turn out to be the same mass I apologize). Let's at least think of each person having a different mass. Keeping acceleration and displacement constant for each hiker and changing each hikers mass would lead to different amounts of work needing to be done to get to the top of the mountain. Next time you take a hike, consider the physics behind it. It's pretty cool.

kateh516

kateh516

 

Mini Golf

While Mini-Golfing with some friends on a trip to Cape Cod over summer vacation, I decided to take a video of a, surprisingly, challenging part of the course. It involved a loop that you could either hit your ball into or try to go around it. For most of us, we ended up hitting into the front part of the steel loop and getting our ball no where. None of us were really playing by the rules so we let each other have multiple shots until our ball finally went through/passed the loop. In preparation for this class, I took video in the hopes someday it would show up here (will see if the attachment works). So, how does the golf ball not fall when it reaches the top of the loop? Physics, of course!! To keep the ball from falling the centripetal force must equal the weight (mg) of the golf ball. Centripetal force is found by multiplying the mass of the golf ball by centripetal acceleration (this equals (v^2)/r). You end with an equation like this: mg= m((v^2)/r) Since the only value that can be controlled by you-unless you want to break your golf ball or smash the loop, both of which would take you out of this situation- is velocity. Changing your velocity is the only way to get your ball to go through the loop without dropping from the top! IMG_1309.MOV

kateh516

kateh516

 

Mucking Stalls

More horsey physics!!! Horses are big animals and with that comes a lot of food that is consumed. Lots of food means lots coming out the other end. Mucking out stalls and pastures is a daily task for horse owners/stable workers. It's not a terrible task, honestly. It gets a bit tiring when you have 20 stalls to clean along with all the other tasks to do around the barn and wanting to ride for a couple of hours. Physics can make the job a little easier. It all comes down to torque. So you have the mass at the end of the pitch fork you are using. The force applied is usually pretty close to the opposite end. It takes a lot of energy to lift the end of the pitch fork up into the air and dump it into the wheel barrow. To make the job easier, you can add a fulcrum (your other hand). The closer it is to the end of the pitchfork, the easier it is to lift. This is because W=Fd. You can apply the same force as you would if the fulcrum was nearer to the top but because there is a greater distance between the force and your second hand, more work will be done, which in turn feels like a lighter load to lift. 

kateh516

kateh516

 

Lasers

It's common for lasers to be included in high intensity, spy movies (so I've heard). I've really only seen them in kids cartoons since I'm not well versed in current movie culture (I really only watch romantic comedies-whoops). KIDS!! You are being fooled! You can't actually see a laser beam when it's pointed across a room. Those red lines that you have to tentatively step around to avoid setting off the alarms would not actually be there in real life. Why is this the case? Well, lasers are very different from everyday light. It has one specific wave length and is very concentrated. You can only see light that enters directly into your eyes. Because the light emitted from a laser travels in one direction, you aren't able to see it. You can't see it until it hits a wall and the light particles are reflected in multiple directions, ultimately entering your eye. Or, you can clap dust into the air and the light particles will reflect off the dust and enter your eye.  So, next time you see a character rolling under and jumping over laser beams, just know that they shouldn't really be able to see them, unless the air there was very dirty.

kateh516

kateh516

 

Wind Turbines

I'm all for reusable sources or energy because, one day, the world will run out of oil and without preparation for that day there will most likely be an energy crisis. It's one of the biggest tasks I think my generation should be taking on. One example is a reusable energy is wind. Wind is cause by the uneven heating of the Earth. Wind power has been harnessed to do work before. Windmills used to be used to grind grain down into a flour. So, how does a windmill or wind turbine work? Well, the wind will be moving at a certain velocity and hit the surface area of one of the blades on the turbine. Energy can be measured in power multiplied by time. So the amount of energy created depends on how much power is created over a certain amount of time. The amount of power created depends on the area the wind hits and at what velocity. Then, due to conservation of energy, whatever energy created by wind can be transferred into another usable form.

kateh516

kateh516

 

Driving in Snow

Yesterday, on the way home from a colleg interview, the weather conditions took a turn for the worse. Luckily, I was not alone, and my mom was able to drive home. What would have been a two and a half hour trip turned into four and a half hours because we had to drive at a much slower rate. We also had to leave a greater amount of space between the car in front of us. Because of how snowy the roads were, there was a greatly reduced coefficient of friction between our tires and the pavement. It takes a greater amount of time to stop when the conditions get snowy or icy. The more room you leave, the greater chance you have of stopping before you hit the car in front of you. 

kateh516

kateh516

 

Christmas Candles

I don't know what it is, but I always seem to have candles burning a lot more frequently around Christmas time than any other time of year (which in my case means more than one time a day which is my norm). Maybe it's the whole lighting of the advent candles at church that influences me. Or maybe I'm a pyromaniac whose tenancies increase in December?? Either way, candles are very important to me and since physics is everywhere, it's definitely in candles! Let's start with the lighting of a candle. I use matches. On the side of the match box is a strip of rough material. When you apply a force to the matchstick as you push it across this strip, the friction in between the tip of the match and the strip causes a release of energy. Due to the conservation of energy, the loss of energy in the match has to go somewhere. As you probably know, striking a match causes flame. Flames create both light and heat. That's where this energy goes. This energy is then transferred to the candle. From here, the candle experiences a phase change. The energy, in the form of heat, continues to add to the stored energy of the candle. When the energy gets high enough, the object begins to break down. So you'll notice as a candle burns longer, it starts to melt due to the addition of this form of energy.  So next time you light a candle- maybe while singing Silent Night in your church's Christmas Eve service, or maybe while writing a blog post- make sure to thank physics for making it possible.

kateh516

kateh516

 

The Good Dinosuar

A few weeks ago, I went to see the movie The Good Dinosaur with some friends. It was a great movie and I definitely think that if you are reading this you should go see it. Since this is a blog about physics, let's talk about that! As the movie begins, a asteroid gets dislodged from the asteroid belt between Mars and Jupiter. This asteroid starts moving directly towards Earth. As it gets closer to Earth, it enters the Earth's Gravitational Field. It bursts into flames as it enters Earth's atmosphere as there is a sudden change from the vacuum of space where there is no friction to the friction filled air. This sudden change causes a change in energy. Energy is lost in the form of heat. The heat is strong enough to cause flames. So it starts off a pretty accurate representation of physics. Then, by some chance, the asteroid misses Earth. This is impossible since there was no force that acted upon it to change it's direction. The asteroid was already feeling the affects of Earth's gravitational pull. The asteroid should have hit Earth, but that would mean the movie would have been over in the first few minutes. So we will have to pardon Pixar's incorrect physics since they did do a good job of telling a story. 

kateh516

kateh516

 

Don't Drop The Eggs

... unless you are instructed to do so by your physics teacher My fellow blogger, zlessard, has also just posted a blog about a similar topic, as we both had to write one up for class. Our mistakes were different but we both had the same goal. The purpose of this lab was to figure out what height the arm on which the rubber band and egg were attached had to be so the bottom of the egg just touched the top of the paper (resting on a table) below it. To find out what height it needed to be, the potential energy of the system had to be determined. Potential Energy (U)= mass (m)*Acceleration due to gravity(g)*height (h). Once potential energy was found, it would be possible to determine the height, since the mass of the egg was known. To find the potential energy stored different masses were used to determine a different displacement of the rubber band as well as the force applied. On earth we know the acceleration due to gravity is 9.81 m/s^2 so the force applied is easy to find (F=ma). When the different masses were added to the rubber band the displacement was able to be found by measuring how far the rubber band. The area under a force vs. displacement graph is equal to potential energy. This is where my group messed up. Instead of integrating by weight, we integrated by mass. This would give us the wrong value for the potential energy causing the rest of the calculations made to find the height at which to drop the egg from. So after integration, you find the potential energy to be .8932J. Then using the equation U=mgh, you can figure out the height, which in our case would be 1.3007m since our egg had a mass of .07kg and the acceleration due to gravity on earth is 9.81 m/s^2. Yesterday, when we dropped our egg we were lucky enough to make an educated guess that was correct. At least, my group has discovered our mistake (integration... it's important) and can move forward with this knowledge.  I highly suggest trying this at home (be prepared to clean up and broken eggs!!!) because it's a great lab to do for fun. Even if you do trial and error drops   You'll need a few rubber bands, a place to attach the rubber band to. And then something to attach the rubber band to the egg. Good luck! 

kateh516

kateh516

 

Cats Using Physics

I believe most living things are born with some a basic understanding of physics. If I jump up, I'll come back down. We certainly know gravity, as it effects us every moment we are on Earth. I'd like to share an example of this. Recently, as I worked on some homework I had, my cat jumped up on the table. She walked around on it, exploring, for a few minutes then went to jump down. I noticed she did not do anything other than simply sliding her front paws off, the rest of her following after gravity took over. When her front paws left the table there was no longer the force of the table acting upon her. The force the table exerted up on her four paws was greater than the force of gravity acting on her in the downward direction. Once that barrier was gone, the only force left acting upon her was gravity. She landed, then trotted off, on some unknown mission that cats often have.  To conclude this blog post, I would like to share a physics joke with you. It involves cats (which is how I'm tying it into this blog). Here goes: Two cats are sitting on a roof. Which one slides of first???     The one with the smallest mew!!! 

kateh516

kateh516

 

Carpet Skiing

The other day, after gym class, a few of my friends (you know who you are... I'm just protecting your privacy) stopped by the locker of one of said friends. His locker is known for the large amounts of food that is kept in there. After emptying out a Capri-Sun* box and a box of Little Bites Muffins* someone had the brilliant idea to put one of the boxes on their feet. He tried skating around on one foot without much success. After meandering along the halls, I thought someone should try wearing both. After a bit of experimentation with that we decided to start pulling each other around. The person wearing the boxes held onto another person who ran along, pulling them behind them. While nervously watching the security guard I was sure was going to approach us to tell us to stop I realized, "Hey! This would make a great physics blog post!" So, let us discuss the physics behind why this extremely fun activity (that, yes, I eventually did try) works!! If you tried to grab on to someone's back and have them pull you with your feet flat on the ground, you would most likely end up not getting very far. This is because the soles of your shoes are made to have a large amount of traction (a large coefficient of kinetic friction) so while you walk you don't slip all over the place. The boxes are the magic catalyst. When you put the boxes on your feet, the coefficient of kinetic friction greatly reduced, so while you are being pulled you can move across the top of the carpeted hallway without getting "stuck". It's also easier to start pulling someone because the coefficient of static friction is smaller that if you were wearing normal shoes. This means it is easier to get someone moving from rest.  I highly suggest trying this with your friends sometime... but please be careful. Sometimes physics can get a little dangerous      *DISCLAIMER: I was not sponsored by either of these companies, nor were any of my friends. I just thought it added to the blog

kateh516

kateh516

 

The Importance of Phone Cases

Since we have moved out of the era of brick phones and indestructible Nokias, and have entered the world of fragile iPhones, the market for good phone cases has widened greatly. Cases used to be just stylistic choice. Now they are almost necessary since you are investing hundreds of dollars into an iPhone (they are totally worth it though). How does the case work to prevent damage to your phone though?  When you drop your phone on a surface, the surface will act with an equal and opposite force on the iPhone. A large enough force is able to dent or shatter a phone, if dropped without any protection. Cases are built so that, on impact, the forces are distributed evenly across the phone. The materials used are also able to absorb some of the forces, again lessening the force that is exerted on the phone itself. 

kateh516

kateh516

 

Stringed Instruments

Guitars, violins, violas, cellos... all examples of stringed instruments. There are many different ways to play them, but for the sake of this blog post I'm going to focus on plucking. Plucking is when whoever is playing the instrument uses their finger to pull up the string and let it go. I believe this is more commonly seen with guitars (I play violin and it doesn't happen to frequently in the pieces I play). All of these instruments have strings that are fixed on each end. When a string is plucked, the string vibrates at a given frequency. The vibration gives off a sound. As you place fingers down on the finger board, you change the length of the string. This will change the frequency (see the equation attached below). As the length changes (represented as lambda) the frequency will change producing different pitches. 

kateh516

kateh516

 

DSLR vs. iPhone Cameras

Nowadays, almost everyone has a camera right at their fingertips. With the invention of the smartphone, even the camera phone (remember when you were the coolest kid if you had a camera phone... or even just a cell phone?!!) pictures and picture taking has become an intricate part of everyday life. We've come a long way from the first ever camera phone to today's iPhone. The quality of the picture has improved greatly while remaining a lot smaller than a DSLR (digital single-lens reflex) camera. An iPhone will always be more convenient and more practical than carrying around a large camera, but the DSLR will take better pictures, hands down.  This may seem obvious to most people. Yeah, a camera is going to take better pictures than the phone will. Let's discuss why this is true. In an iPhone, the lenses used are fixed. They do not have the capacity to zoom. The zooming you see on your screen is a digital zoom. The computer part of the camera takes the image and makes it larger. In a DSLR, the lenses rotate so that the focus is clear even after zooming a large distance. The DSLR lenses move individually so that the light being focused on the digital processor in the back of the camera is in it's best form. The mix of concave and convex lenses are what allows the camera to achieve the best possible zoom, and maintain the highest image quality. The iPhone is just to small to allow for space that would let the lenses move by themselves. They have to fit within a fixed amount of space. Yes, the iPhones have gotten larger in the past few releases (compare the iPhone 4 to the iPhone 6 plus- HUGE difference) but not enough to have a camera capable of what the DSLR is.  So, DSLRs are a good investment for special occasions, but the iPhone will never be replaced by a DSLR simply because the iPhone is a more practical, everyday device. 

kateh516

kateh516

 

Dropped Waterbottle

Today as I was rushing out of the house to my car, I dropped my water bottle on my driveway. As it hit the floor and bounced back up to me, I realized that it was an inelastic collision!! Actually my first thought was to get it from under the car so I could take it to school, but that's besides the point. Anyways, I knew it was an inelastic collision because some of the energy the water bottle started with, which was all potential energy because it was not in motion yet, was changed into sound energy as well as the energy used to create a dent in the bottle. So, the water bottle starts off with PE=mgh then is dropped and the energy changes into kinetic. When it hits the floor, the loss of energy is experienced as the bottle is deformed and the noise is heard. Due to conservation of energy, the bottle keeps some energy as not all of it is dissipated which is why it bounces back up off the ground.   

kateh516

kateh516

 

Getting "Left Behind"

On Saturdays I usually have a riding lesson, which is always the highlight of my weekend. On my drive home from the barn, I was reflecting on the lesson and what I could improve on for next week. The goal of riding is to make all your cues to your horse invisible and move with the horse as much as possible. Sometimes, after asking for a faster speed from their horse, a rider gets "left behind"- as the horse gets faster the rider doesn't move with the horse and look like they aren't moving together. It can happen when the rider asks and is off balance or unprepared for the change or sometimes, as in today's case, you are riding a young (in the horse world it's called "green") horse. The horse I was riding today, Mystic, decided a few times to go a little bit faster than I had anticipated so I got left behind. After taking him over some ground poles at a trot, he started cantering (a faster speed than a trot). I could have helped him by making my clues more clear. In any case, on my drive home, my reflections turned to the physics of the matter. An object in motion wants to stay in motion, initially. When riding, two objects are trying to act as one, but when the horse changes speeds abruptly, the rider continues to move at the previous speed causing him or her to get "left behind". It's sort of like when you step on the brakes of the car and come to a stop really quickly, your body lurches forwards because it's trying to move at the same speed as it was before. The seat belt keeps you in place. With riding, it just works in the opposite direction with your body moving slower and the horse moving faster. And there is no seat belt keeping you on

kateh516

kateh516

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