Tuesday, September 19, 2017

The Physics of Football: Beast Mode Edition

This Sunday, like most, I followed my routine of watching NFL games and keeping up with my fantasy football teams. While I was sitting on my couch watching 220-pound behemoths collide in the open field, I wondered how the motion of these players related to physics.

When it comes to running styles in the NFL, coaches consistently preach “north-south” running instead of “east-west” running to ball carriers. With respect to kinematics, coaches prefer their players focus on the y-component of their motion instead of the x-component. They focus on the differences between distance and displacement. If a first down is 10 yards and solely measured by a runner’s displacement in the positive y-direction, and the vector of the displacement of a runner is 10 yards east and 3 yards north, ultimately they are well short of a first down. Therefore, it is understandable that coaches preach “north-south” running because it allows runners to maximize their displacement in the y-direction, which is most important for gaining yards in the game.

Conversely, offensive linemen tend to move in a different manner. A lineman’s job is to move defenders to create running lanes for the halfback. Because of this goal, the motion of linemen can often have a more prominent x-component, as they are tasked with making contact with a defender and then angling them in either the +x or the –x direction away from the runner.

Image result for 17 power football playI wanted to particularly analyze the motion of Marshawn Lynch in his infamous "Beast Mode" run from the 2011 wildcard game between the New Orleans Saints and the Seattle Seahawks (video below). In the video, we see Marshawn Lynch rip off one of the most memorable runs in NFL history. If we look at the play below we can think of the motion of each player as a vector within an x,y coordinate system. We can see that the direction of the blocks from linemen and receivers contains a substantial x-component as they angle off defenders and create a hole for the running back. The vector of the halfback’s motion demonstrates a nearly vertical trajectory, following the “north-south” running style NFL coaches value. Thus, Lynch was able to grind his way to a touchdown by ensuring he runs in the +y direction and maximizes his displacement as he moves forward. 

Theory of why the traditional gender gap exists in physics

There is not a doubt that there is a gender gap in most STEM fields, especially in physics. Australian academics have put forward an interesting theory about the gender divide in physics and hypothesise that it is because of "boys' fondness for urinating at targets." Due to this hobby, boys are able to understand force, momentum, fluid dynamics, and other key concepts of physics better. Although they cannot prove this theory without empirical evidence, they think that this "self directed, hands-on, intrinsically (and sometimes extrinsically and socially) rewarding activity must have a huge potential contribution to learning, resulting in a deep, embodied, material knowledge of projectile motion that's simply not accessible to girls."

They argue that physics is a difficult subject for girls because they lack the experience of grasping projectile motion first hand. It is usually taught in the beginning of physics courses because it is a relatable concept, like throwing a ball. Since boys stand up and have "playful urination practices," they may have an advantage over girls in understanding physics. They do offer more traditional explanations for the gender gap, like the problem of society associating logical and mathematical ways of thinking with masculinity, and some parents or teachers may inadvertently discourage girls from pursuing STEM subjects.

This study started because in the UK, 1/5 students who studies "A-level" physics is a girl. When conducting this study, they found the differences were pronounced when asking questions about projectile motion that focused on the velocity of objects that are thrown, kicked, or fired. In order to combat this gender gap, specialists have suggested changing the curriculum so that forces and momentum are not taught first, and to put a slighter emphasis on projectile motion. They don't suggest that girls also start "playful urination practices" but they do start with subjects like energy conservation, which they claim is more central to physics.

Thursday, September 7, 2017

How the use of the iPhone 9 minute snooze button affects the speed of getting ready in the morning

I am a notorious alarm clock snoozer and in the morning that can leave me with a frantic 30 minutes or less to get ready for the day. I wanted to see how long it would take me to get ready without using the alarm clock snooze. I hypothesize that the shorter time I have to get ready the more steps I will take because I will start to get frazzled and try to do too much with the shorter time I have. This increase in steps and distance traveled but because I have less time the speed in which I get ready will increase from a morning that I do not snooze. For this experiment, I will be using my IPhone as a pedometer and as a stop watch. On Tuesday morning, I did not snooze the alarm and I got ready in 40. minutes. On Thursday morning, I snoozed the alarm two times and had 22 minutes to get ready.

The day I did not sleep in resulted in a 81 percent increase in time that it took to get ready compared to the day I slept in. I walked 40. percent more when I was rushed compared to my normal morning routine. Overall this lead to a 167 percent increase in speed. This increase in all areas seems to make sense because in the morning as time gets more constrained I feel myself becoming more frantic. This leads me to start going out of order in my routine and running around with no purpose. This unnecessary movement and the already constrained time leads my speed in the morning to be increased by almost three times my morning routine.

Physics of Star Wars book explores the science of the force (and gungans)

The first movie I ever saw in theatre was The Phantom Menace in 1999. I don't remember much of it because I was so young, but I do remember being fascinated by the light sabers and, although the CGI technology was no where near as good as it is now, it still amazed me. How cool would it be to live in a world where we could travel at hyper speed through space, and we could have light sabers to fight with. Now with technologies like the hyper loop coming to play, maybe we aren't so far from the sci-fi universe that we all dreamed of as kids.
This article speaks about the "tantalizing and impossible" physics behind Star Wars, evident in the use of the light saber and hyperspace travel. Professor Patrick Johnson wrote the book The Physics of Star Wars to explore if the physics is close to becoming reality. This book will be released November 7, 2017, but is not the first time that a scientist has tried to grapple with this idea. For example, in 2016, Mark Brake and Jon Chase wrote the book The Science of Star Wars: The Scientific Facts Behind the Force, Space Travel, and More! along with several other similar publications. 
Each chapter explains one phenomenon, how it fits into Star Wars, and then how it works compares to the physics that we understand in the real world. 
The example the article draws on is that there's one chapter about machines making machines, which seems like a soon reality since we already have 3D printers and automated manufacturing plants. 
Circling back to The Phantom Menace, they travel to the core of Naboo, and when they do this, the movie implies that Naboo is water from "surface to surface," and it is possible to have a planet like that, but has certain implications that Star Wars did not entirely consider. For example, the water at the bottom would be under high pressure, and more likely to freeze since the boiling points of water change with pressure. And now that you consider that, will the radius of the planet be affected by that? He said, "If you go to the perfect center of a planet there's no force of gravity because on all sides it would be pulling it towards it, so there's no force of gravity. This means that the pressure behaves in a more complicated fashion as compared to my initial approach." And then, if Naboo was truly water at the core, then it wouldn't have the iron core or a magnetic field, but then maybe the inhabitants set up a magnetic field on their own, or they are super resilient to radiation. 
Physics in pop culture is incredibly interesting and I'm so excited to read this book!

Sunday, December 11, 2016

The Physics of a Slap Shot

One thing that has always fascinated me is just how hard a hockey player can hit a slap shot. In baseball, exit velocities on hits can reach up to 120 miles per hour, Giancarlo Stanton of the Miami Marlins pushed past that threshold to 123.9. By comparison, hockey slap shot has topped out at 108.8 miles per hour, thanks to the massive build of Bruins defenseman Zdeno Chara. This makes sense though, a baseball arrives at the plate anywhere from 75 to 105 miles per hour, and a bat swing can have high velocities near that too. So in the collision of the bat hitting the ball, there is a huge Impulse. In hockey though, a slapshot is usually launched from a standstill, or off of a soft, controlled pass. So I wondered, where does all of the energy come from in a slapshot?

SmarterEveryDay, a YouTube channel that focuses on these types of real world questions, helped to enlighten me on where all of this energy comes from. When a hockey player fires a slapshot, they don't hit the puck cleanly. If they were to do so, then the only energy that would be acting on the puck would be that applied by the player. Now, some of these hockey players are big dudes that can swing fast, but there's a maximum human threshold. In order to put more power behind the puck, one would have to look at the stick. Today, sticks are designed to have a certain amount of bend to them. This bend not only keeps the stick from breaking, but adds a whole new type of energy to the swing. Instead of hitting the puck clean off the ice, a hockey player will instead hit the ice first, which bends the stick back as much as a few inches, and then as they follow through, the generated elastic potential from the bending stick is unleashed on the puck, lengthening the collision, and exerting more energy. It all happens in a few milliseconds, but that momentary drag on the ice makes all the difference.

Check out the video here! It's really cool to watch for hockey and physics fans!


Saturday, December 10, 2016

Bernoulli Equation and Trains

After learning about Bernoulli Equation I recalled a situation that occurred early in my life. While waiting for the subway in NYC as mischievous 10 year old I always would stand near the edge of the platform before the train would come in. My mother, much to her credit, would always pull me back and berate me saying that the train could suck me in if I stood that close while the subway came by. As I know it all 10 year old I would laugh at this suggestion. Using Bernoulli's Equation however, it is possible to see if my mom was right.


Since we have no change in height and we are looking at the change in air pressure the equation we use becomes:

       Δp=(1/2)p(v1^2)-(1/2)p(v2^2)            p(air)= 1.225kg/m^3    v(air)= 500m/s                                                                                                      v(average subway)= 24m/s

      Δp= ((.5)( 1.225kg/m^3)(500m/s)^2) - ((.5)( 1.225kg/m^3)(524m/s)^2)=-15,052 N

Rearranging P=F/A to F=PA and assuming the average area of person is 1.7m^2 we get:

         F=(15,052N)(.85m^2)= 12,794N                *since the air pushes only on half a person's body the                                                                                  area used is multiplied by a factor of 0.5.

12,974 newtons would certainly be enough to move a small child though bear in mind that to fully experience this force an individual would need to be a the entrance to the tunnel and extremely close to the train. The force would dramatically decrease as the distance between an individual and a train increased. Even so it is not advisable to stand near a moving train, and I guess one should sometimes listen to their parents.

Earth's Rotation Is Slowing Down

According to a study, Earth's rotation's been slowing down by 1.8 milliseconds each century due to tidal friction. Thus, I wanted to calculate how long it would take for Earth to reach a rotational speed where a day would begin to last 25 hours, and how fast it is decelerating (in rad/s^2).

If the rotation slows by 1.8 milliseconds (1.8 x 10^-3 s) per century, the time it would take for the rotation to gain an hour (from 24 to 25 hours) would be quite long:

# of centuries = (3,600 s)(1.8 x 10^-3 s)
# of centuries = 2,000,000 centuries

This is essentially 200,000,000 years before Earth's rotation time increases by an hour. 

Next, I assumed that Earth's current rotation time is exactly 24 hours or 86,400 seconds. In order to calculate Earth's current rotational velocity, I used the following formula:

ω = ∆θ/∆t
ω = (2π)/(86,400 s)
ω = 7.2722 x 10^-5 rad/s

If each day lasted 25 hours (90,000 seconds), Earth's rotational velocity would be the following:

ω = ∆θ/∆t
ω = (2π)/(90,000 s)
ω = 6.9813 x 10^-5 rad/s

Using these numbers, I then calculated the rate at which the rotation is slowing down in rad/s^2:

200,000,000 years x 365 days/yr x 86400 s/day = 6.307 x 10^15 seconds

ωi = ωf + αt
7.2722 x 10^-5 rad/s = 6.9813 x 10^-5 rad/s + α(6.307 x 10^15 s)
α = 4.612 x 10^-22 rad/s^2