# srossi14

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1. ## Tipsy

Did anyone else watch that show Minute to Win it? As I was trying to think of something the write my last physics blog post about I thought of one task in particular that contestants were asked to complete. The game was called “Tipsy.” To win, the contestant had to balance three soda cans on their edge by drinking some of the soda to the perfect level. The reason that this task is possible is because of physics and center of gravity. As the amount of soda in the can decreases, the center of gravity of the tilted can shifts as the weight of the can changes due to less liquid, and eventually it is able to align with the vertical line up from the balanced edge of the can. So I was going to just attach a video of the "blueprint" for the task but I found a video of a bunch of college students getting real hype about it so I decided to include that instead:)
2. ## The Suspense is killing me

A couple of years ago, my family traveled to San Francisco and one thing we did was see the Golden Gate Bridge. To my disappointment, it was not that bright red that you might see in pictures. Anyway, the Golden Gate Bridge is a suspension bridge that is about three miles long and crosses the San Francisco Bay. With such a massive structure, one might wonder, how on earth does it stay up? Well, it has to do with the “suspension” part. By connecting cables to the middle of the bridge, up to towers, and back to the ends of the bridge, it decreases the force of the weight of the bridge in the middle, by creating a force upwards from tension. This way, the middle of bridge doesn’t collapse, and the bridge stays structurally sound. Unfortunately though, the suspension cables don’t protect the bridge from getting destroyed in a multitude of movies.
3. ## New York City Cabs

Everyone knows that it’s a nightmare to drive in New York City, even if you don’t drive yourself. When I was there last weekend, because we flew there, we had to use cabs and the subway to get around. We encountered many shall we say…interesting drivers. One was yelling at the other cars in a different language, but one of my favorites was the one who thought it was a good idea to drive 60 mph down the streets of Manhattan at 11:30pm. This made for a thrilling trip back to our hotel. Unfortunately for the driver, and us, there were other cars on the road at the time, and people, and stoplights. This meant there were a lot of sudden stops. As stated in Newton’s first law of motion, an object in motion tends to stay in motion, even if it’s in a small metal deathtrap of a car. So when the cab came to a sudden stop, us passengers wanted to continue moving forward at 60mph. So when we wanted to keep moving forward, the seat belts provided a force in the opposite direction, keeping us in our seats...and the car. Let’s just say thank goodness for seat belts.
4. ## More Sherlock Physics

I’ve already talked a bit about the show Sherlock, but I realized that there is a lot more physics involved to talk about. In one episode, called His Last Vow, Sherlock is shot in the chest. It’s a bit complicated to explain, but in the moments of shock following, he processes what he has to do in order to stay alive. The first decision is whether to fall forward or backwards. Because the bullet didn’t go completely through him his best option is to fall backwards to reduce blood loss. However, because of physics, and conservation of moment, wouldn’t he fall backwards anyway? It would be like those bullet and block problems that we did so much in physics last year. If the bullet was moving toward Sherlock, and he was facing the shooter, because of the velocity and direction of the bullet, and Sherlock’s stationary position, when hit, the momentum of the bullet would push him backwards as well. Maybe the bullet’s momentum wouldn’t be enough to do so, or maybe, the Sherlock writers didn’t think enough about the physics.
5. ## Braking Planes

This past weekend my family flew to New York City, and as I thought about all the blog posts I had left to write, I tried to figure out what I could write about. And then, as we were landing, I realized that there was a lot of physics in the way a plane stops. Planes are able to travel at extremely high speeds and stop fairly quickly. What I didn’t know though, was what was used in planes as a braking system. It turns out that this can very with different planes. Some use a reverse thrust system, which means that the engines will kind of work “backwards.” By applying a force backwards, the equal and opposite reaction is for the plane to slow down as two forces work against each other. There are also speed brakes on the wings of the plane, which are the parts that flip upwards when landing. These increase drag, which also allows the plane to slow down.
6. ## Game On

When playing tennis, one way to control your shots is by putting spin on a ball. Tennis players do this by applying a force to the ball in different ways. This produces a different torque on the ball, changing its path after it bounces. If a ball is hit “flat” it is pretty predictable that the ball will bounce back at the same angle that it landed. To eliminate some of this predictability, a player can hit different shots that add top spin and back spin. When a player is at net, and their opponent is on the base line, a smart decision might be to hit drop shot. When a drop shot is hit, the torque is applied downward at an angle, which causes the ball to travel forward, but spin backwards. This means that when it lands and bounces back up due to its momentum, the ball will bounce back up, but more away from the opponent and back towards the net. By using physics and torque, tennis becomes much more interesting to play and watch.
7. ## Col Legno

As string player, one way that we can change the sound of the instrument is by playing “col legno.” This means that instead of using the side of the bow with hair on it, sound is made by bouncing the wooden side of the bow on the string. This provides a less lyrical and quieter sound. The reasons behind this change in sound are because of physics. The wooden side of the bow has a smooth surface, which contrasts the surface of the bow hair greatly. Bow hair has tiny grooves in it, which is ten covered in rosin to make it stickier. The wooden side of the bow does not have this. Therefore there is less friction between the surface of the string and the back of the bow. Because there is less friction, the force from the bow that acts on the string to make sound is much less as well. Because of physics, string players are able to change the sound of their instruments.
8. ## Even more swing physics

Who didn’t jump off swings when they were younger? Even as little kids, we knew that the best time to jump was when the swing reached it’s greatest height. By doing so, the maximum amount of gravitational potential energy is converted into kinetic energy when the person becomes a projectile. At a higher height, the velocity of the projectile is greater. If one were to jump off a swing at a lower height during its oscillation, the angle of projection would also be smaller. This could possible lead to the person landing underneath the swing, only to be hit in the head when the swing comes back, because it is an example of simple harmonic motion. So, whenever you’re on the playground, remember your physics, and avoid head injuries!
9. ## Bubbles

The other day, my seven year old cousin asked me, “how do bubbles work?” and I didn’t really know how to answer. So, I decided to answer her question in a blog post, or at least try to (even though she’ll never see it). It turns out the science behind soap bubbles is a bit complicated and there’s a lot that can be talked about but I think I’ll just focus on one part for now. Did you ever wonder why bubbles are always spherical? Laplace’s law states the larger the vessel radius, the larger the wall tension required to withstand a given internal fluid pressure. In the case of soap bubbles, the soap film minimizes its surface area, and by doing so, minimizes the surface tension of the film. The shape that allows for this minimal surface area is a sphere. I know this is a bit convoluted, but who knew bubbles were so complicated?
10. ## More on tire swings

If you happened to read the previous post about tire swings, hi, I’m the short friend! Anyway… I also noticed that the tire swing was a perfect example of physics in the real world. Tire swings are an example of simple harmonic motion, a pendulum to be exact. When the tire is lifted to a certain height and let go, it swings back and forth, ideally at the same height each time. However, because this is not a perfect world, and factors such as air resistance came into play, this was only somewhat true. Also, with pendulums, the weight of the object on the end of the string/rope does not affect the time it takes to make one “revolution”, only the length of the pendulum. This means that in theory, it would take the same amount of time for a certain 6 ft 2 in person to make one revolution on the tire swing as a person half her height.
11. ## More Violin Physics

When you think about string instruments and physics, the thing that most people think about is the vibration of the strings to make a sound. Notes can be changed by placing fingers at certain intervals to change the length of the string. But another way to change the sound of a violin, is by using a mute. A mute is most commonly made of rubber, and attaches to the bridge of the string instrument. When attached, it adds weight to the bridge and changes the fundamental frequency of the bridge, which also vibrates when the instrument is played. The result is a softer sound, and a muted tone. In orchestra’s mutes are often used when there is a soloist playing with the ensemble. By using mutes, the full orchestra can still play without overpowering the soloist. However, some instrumentalists prefer not to use a mute because it changes the tone quality. But in other cases and for other instruments, mutes are used for different music genres resulting in a greater variety of music possible.
12. ## Surfing

Over the summer, I had to chance to take a surfing lesson. Surfing requires balance, and coordination, so I was not particularly good at it. One very important aspect of surfing was going from laying down on your stomach, into a standing position. When doing this, it was very important that you were in the right part of the board, so that you were at the center of mass of the system. If you were too far back on the board, the force of the wave moving forward could pull the surf board up and out from under you throwing you backwards. It was also important to keep your body, and center of mass low. If you stood up completely straight, and then moved from the center of mass, the torque experienced by the surfboard system will be greater because the “radius” from the axis (the height of your body) is greater. So based on physics, I shouldn’t have had too much of a problem with surfing, oh well.
13. ## Sailing

Recently we talked about flux and Gausses law. One thing that flux was compared to was the air of a fan hitting a wall. This could also be applied to sailing in a similar sense, even though it doesn’t involve electric fields. Electric flux is the electric field multiplied by the surface area of the plane the e-field is traveling through. When wind hits perpendicular to a sail, the force causes the boat to move. When it gets particularly windy, to prevent the force of the wind from causing the boat to keel over, the mainsail can be shortened. The action of bringing the sail down lower decreases the amount of surface area that the wind can push against. By decreasing the surface area of the sail, the “flux” will also decrease. So even though this isn’t exactly the same, the concepts are similar.
14. ## Here's the kicker

So I’m sure you’ve all seen it, but if you haven’t you should. A couple weeks ago, the Buffalo Bills kicker was seen on the sidelines slamming his football helmet to the ground after missing a field goal. After doing so, the helmet bounced off the ground, and hit him in the face. I won’t pretend to know anything about football, but I did see this, and I’m not going to lie, I watched the video multiple times. But this embarrassment could have been avoided if he had just known physics and been familiar with conservation of momentum. Momentum is equal to the mass of an object times the velocity, and conservation of momentum states that the momentum of a system is constant. So whatever velocity the helmet was thrown, is the velocity that it would bounce back up with. Because he was pretty angry, I’m guessing the force he applied was quite large, making the velocity pretty large also. So the result of his action could’ve been predicted. He should’ve studied more physics in college…
15. ## Canoe believe this?

Canoeing is an activity that requires a lot of upper body and core strength, that and kayaking. When you use a paddle to propel an objet, you are applying newton’s laws of physics. Newton’s second law of physics states that acceleration is dependent on mass and the force acting on the object. Newton’s third law states that for every action there is an equal and opposite reaction. Both of these laws can be seen in canoeing. When the paddle is placed perpendicular to the water, and a person pushes against the water in the backwards direction, the result is the canoe moving forward, opposite the direction of the force applied as newton’s laws state. And like everything else, the greater the force applied, the greater the acceleration, and the greater the velocity. So next time you go canoeing or kayaking you’ll know that physics is the reason paddles work!