Hoverboards: Are we there yet?

As the year of 2015 draws to a close, many fans of the beloved classic, Back to the Future, bemoan the fact that in 2015 we have not created all of the wonderful inventions that had been promised via Marty McFly's adventures. However, I did some digging and found some very promising prospects on the creation of a hoverboard. Three types of hovercraft, that actually function as we would a hoverboard would, are currently on the market. Two of these hovercraft, the Hendo and Lexus, rely on magnetic fields for the source of repulsion necessary to overcome the force of gravity. The other hovercraft works like a small helicopter, using thrust generated by blades moving air at a high speed.

In a quick calculation I determined how much force would be necessary for a hoverboard to lift a person off of the ground. For a person weighing 70 kg to stand on a 5kg hoverboard, their force due to weight would be about 735 N. In order to lift that person into the air, the force provided by the craft must be more than 735 N.

The other option for a "hoverboard" comes from the self balancing motorized scooter. It works using pressure plates, infrared detectors, and a gyroscope. By adjusting the rpm and angle of the wheels based on the movement of the person standing on the board, the "hoverboard" allows the person to move about without handles or any outside force exerted by themselves. The issue with these is that since the "hoverboards" are so popular in demand there has been an increase in their cheap manufacture, which leads to the use of cheap parts. Since lithium batteries are now being produced cheaply (and poorly), these cheaply produces "hoverboards" are provided cheap lithium batteries that are more prone to short circuit and combustion. For this reason, these boards have been banned from airports.

So maybe we haven't perfected the hoverboard yet, but we seem to be on the path to creating a cool new way to travel!

http://www.detroitnews.com/story/business/autos/chrysler/2015/11/27/viper-acrs-record-shattering-tour/76476364/

            In this article, there is a discussion of the new Dodge Viper ACR, and how recently it has been decimating lap times of super and hyper cars supposedly much out of its leagues. It has been decimating records held by the top Porsches, Lamborghinis, Ferraris, etc. This is quite impressive due to the fact that one of these fine cars could be yours for more than half the price of the previously mentioned vehicles. What makes this car so effective?

            The ACR has one of the most advanced aerodynamic systems ever designed on a performance car to this date. It generates a tremendous amount of down force which is the key to its success. This down force created means that the air that passes over the car is channeled in such a way that it pushes the vehicle, specifically the rear wheels where the power is generated, into the road. This allows for more grip and more friction with the rear tires which means that more of the power made by the engine will be able to be transferred to the road. Also, this increase in proper air flow allows for better cornering and handling as well, which too would improve lap times.

http://www.indiancarsbikes.in/auto-news/inferno-exotic-car-the-first-mexican-hypercar-136562/

            In this article, there is discussion of a new ‘Hyper Car’ in the works, coming from Mexico. The new car called the “Inferno” with a very impressive claimed 1,400 horsepower, a top speed of 245 miles per hour, and arguably most impressively a 0-100km/hr time sprint in the sub three second period. These are very astounding numbers in the automotive performance world. What is most interesting about this car however is the material it is made out of. Supposedly the Inferno is composed of a body made of a “metal foam,” which is comprised of a mixture of silver, aluminium and zinc. This is supposedly an astoundingly light yet still strong compound.

            The physics behind this come from the performance figures. I believe that this cars extremely impressive statistics are due in most part to the ultra light composition of the body. That coupled with an engine that produces a massive amount of force, it is not surprising that is putting up statistics that only the top 5% of sports cars make. It will be interesting to see a fully produced model once they are off the line.

Steamy noodles

Since I'm really not creative when I'm cooking, I often resort to making pasta for dinner. As I drain the noodles, a huge rush of steam comes pouring out and is extremely hot and super painful, leading to a depressing mess of noodles in the sink. Having just learned about latent heat, I decided to look up whether steam burns, of which I have been vaguely warned by my mother when desperately trying to teach me how to cook, can be worse than just water burns. Because I have definitely had steam burns that seem to hurt much more than spilling tea or coffee on myself.

It turns out that in fact steam burns can be much hotter, and therefore much more severe than water burns. Since the heat in steam can be increasing while the state of matter doesn't change, it can get much hotter than just the minimum temperature to get to the gas state. Steam can be hotter than water, and in this case the noodle water happened to be boiling. So it can potentially get quite painful without you even knowing it.

Moral of the story: Be careful with ya noodles, everyone.

Bear on a tightrope

I saw this video on YouTube and was fascinated by it.

The bear and the person can move on the thin rope due to the large moment of inertia created by the huge mass of the bear and person.Assuming the mass of the person is 70 kg, the bike 180 kg and the bear, 200 kg with a height of 1m. Assume the person is 3m away from the tightrope. If they are both treated as point masses, the moment of inertia will be;

I = 70(3^2) + (100+180) (1^2) = 910 kgm^2

This is a large moment of inertia and would help keep the system in balance so it does not topple over.

Leaf blower

I found this exploring the internet and decided to figure out the man's top speed before he falls. He appears to have reached his top speed after seven rotations in 4.5 seconds. I approximate the chair to have a diameter of about half a meter, so r=0.025m. Since circumference = 2(pi)r, he rotates seven times, and Δl = rΔtheta, Δtheta = 44.8 rad. From this, I can use kinematics to find the angular velocity. Thetaf = 0.5at^2 + w0t + theta0 --> a (angular acceleration) = 4.42 rad/s^2. wf = w0 + at --> wf = 19.89 rad/s which is 3.17 rev/s

Preparation is Everything - Good Luck With Finals!

Studying got you feeling down? Watch the video below to witness a ferret's unfortunate encounter with physics to cheer you up! *No ferrets were harmed in the production of this video*




One of the reasons why the ferret failed to jump to the other ledge was because he did not have an initial velocity, so he had no kinetic energy. He would need to build up momentum, or have some kind of velocity, to travel from one ledge to the other. But he started from rest and relied only on the force of his hind legs that he used to push off of the desk, which wasn't great enough to get him very far. We can also conclude that this ferret did not have a net work because he had no kinetic energy (no change in velocity) and no potential energy (no change in height between the ledge he jumped from to his destination). The force of his legs was also not enough to get him to the other side because he had no velocity, therefore he had no acceleration.
This is an example of physics gone wrong. But this goes to show that preparation is key to reaching your goals. Just keep up the momentum (your kinetic energy) and you'll go far... unlike this ferret! :)

The Physics of the Spikey Shower Curtain

    

       I was getting my daily dose of internet nonsense and came across quite the interesting product. Below is a picture of a shower curtain that is designed to force people out of the shower after 4 minutes by slowly inflating spikes during the duration of the shower. My initial thought was “OH wow, I need this!” but soon thereafter I began to wonder about the physics of this shower curtain. As it turns out, even in the 21^st century Bernoulli’s principle still inspires a plethora of products.

         Bernoulli’s principle states that an increase in the velocity of a fluid leads to a decrease in the pressure of the fluid. Applying this concept to the shower curtain explains why the spikes inflate over the time one is in the shower. The curtain creates a barrier between the bathroom and the shower, which are of the same pressure before the water is turned on. Once the water is on, the falling fluid increases in velocity as a result of gravitational acceleration. This increase of the velocity of the fluid on the shower side of the curtain leads to a decrease in pressure as indicated by Bernoulli’s principle. There now is a pressure gradient between the shower and the bathroom, with the pressure in the bathroom being greater than that in the shower. The lower pressure in the shower cannot sustain the push of the pressure from the bathroom, resulting in the gradual inflation of the spikes caused by the greater pressure outside of the shower.

A Look at Goal Kicks in Soccer

I've been playing soccer for my whole life, so I decided to study goal kicks, specifically those taken by professional soccer players. I estimated that on average, when a goalkeeper takes a goal kick, they kick the ball 55 meters across the field at an angle of approximately 45^o. With this information, I decided to use physics to determine the initial velocity that the ball must be kicked at in order to reach 55 meters. I was also able to find the maximum hight that the ball would reach during its trajectory, as well as how long it would take for the goal kick to be completed. For the purpose of solving this problem, I ignored air resistance, and therefore this became a projectile motion problem. I also took into consideration that the average length of a professional soccer field is 110 meters. I began this problem by writing down the X and Y components:

X components	Y components
a = 0 m/s2	a = -9.8 m/s2
x = 55 m	y = ?
vx = vcos45o	vy = vsin45o
t = ?	t = ?

Since this is a projectile motion problem with no air resistance, we know that the ball will hit the ground with the same velocity as its initial velocity, but in the downwards direction. Therefore, the initial and final velocities in both the x and y directions will have the same magnitude. Knowing this, I used the Y components to solve for the velocity of the ball in terms of time:

v_f = v_o + at

-vsin45^o = vsin45^o + (-9.8 m/s²)t

-2vsin45^o = -9.8t

t = (-2v(.7))/(-9.8)

t = .14v s

Then I used this answer, in addition to the X components, to find the velocity of the ball:

x = v_ot + ½at²

55 m = (vcos45^o m/s)(.14v s) + ½(0 m/s²)(.14v s)

55 = v²(.098)

v² = 561.22

v = 23.7 m/s

Therefore, the time of the soccer ball’s trajectory would be:

t =.14v

t =.14(23.7 m/s)

t = 3.32 s

Then I separated the velocity into its X and Y components:

X: 23.7cos45^o = 16.59 m/s

Y: 23.7sin45^o = 16.59 m/s        

Using this information, I found the maximum height that the soccer ball would reach during its trajectory:

v_f² = v_o² + 2ay

(0 m/s)² = (16.59 m/s)² + 2(-9.8 m/s²)y

0 = 275.23 – 19.6y

y = (-275.23 / -19.6)

y = 14 m

How to Win a Bet with Physics

How to Win a Bet with Physics

In a survival show an engineer used a rock and a watch to predict depth of a cavern in order to win a bet. He did win the bet with his estimate being right on target. I believe he used physics to do this. He said the depth of the cavern was 80ft. Is this a feasible way to calculate height? If so could this feat be accomplished with physics?

h= v0t x .5at^2

v0=0

t=2.25

a=9.8

h= .5(9.8)(2.25)^2

h=(4.9)(5.06)

h=24.8m

h=81.4 ft

It seems he did use physics!! They used a rope and measured the cavern at about 82ft this means this is a feasible way to calculate depth.

I replicated this in my dorm down the staircase to check the accuracy of this method for myself, and I found:

h= .5(9.8)(1.45)^2

h= 10.3m or 32.8 ft

measured value equals 35ft. This method is accurate enough because 2 ft is a jumpable distance when climbing.

Antonio Brown's Celebration

This Sunday, Antonio Brown scored a touchdown in an NFL game between the Pittsburgh Steelers and the Indianapolis Colts.  After scoring, Brown performed one of the most bizarre and potentially painful celebrations ever:

I decided to find the force exerted onto Antonio Brown by the goalpost.  I started my analysis of this celebration by finding Brown's speed before his goalpost collision.  I approximated this as his average velocity as he ran through the end zone (10 yards).  

v = ∆x/∆t = (10 yards) / (19 s-17.5 s) x (0.91 m) / (1 yard) = 5.7 m/s

Then, I used this to calculate Brown's momentum before the collision:

(Antonio Brown's mass: 82 kg)

p = mv = 82 kg x 5.7 m/s = 467.4 kgm/s

Then, I used his momentum and the time of the collision to calculate the force:

Time of collision: 0.2 s

∆p = -467.4 kgm/s (Brown and the goalpost combined have a momentum of 0 after the collision) = F∆t = F(0.2 s)

F = -2337 N = 525 lb

Thus, Brown felt considerable force during this collision.  It likely would have been very painful.  

Why You Have to Hold Your Gun Right When You Shoot

The conservation of momentum is one of the basic principles we have learned in class so far. Here we shall see how it applies in a gun shot. Even though it is not a common everyday event, a gun shot can be used to analyse the application of conservation of momentum in our surrounding. An unfortunate manifestation of this concept is shown in the video below.

Here we see that the person held the gun very close to his face which resulted in him being hit in the face due to the recoil of the gun. This can be explained by the use of conservation of momentum as follows: 

• Before the gun was shot, both the gun and the bullet inside are at rest so their momentum is 0.
• When the gun is shot the bullet that has a mass of 5 grams will attain a speed of 965 m/s. This will result on the movement of the rifle in the opposite direction as shown below:
  
  
  M1V1 = M2V2
  (0.005 Kg)*(965 m/s) = (3.5 Kg)*V2
  V2 = [(0.05 Kg)*(965 m/s)]/(3.5 Kg)
  V2 = 13.78 m/s, towars the man's face
  
• Assuming the guy held the gun 30 cm away from his face, we can get the acceleration of the gun as it reaches that speed while traveling the 30 cm distance to hit the guy in the face.
  
  

  (Vf)^2 = (Vi)^2 + 2*a*0.3m

  (13.78 m/s)^2 = (0)^2 + 2*a*0.3m

  a = [(13.78 m/s)^2]/(0.6 m) = 316.74 m/s^2
• Therefore, the amount of force exerted on the mans face by the rifle of mass of 3.5 Kg can be calculated as follows:
  

  
  

  F = m*a

  F = (3.5 Kg)*(316.74 m/s^2)

  F = 1108.60 N
  

This shows us that we have to be careful about the way we hold a gun if we ever get to shoot one. Otherwise, the amount of force with which it will hit us may cause problems.

The Physics of Santa

The biggest question in a kid’s mind is how Santa delivers all the gifts in a single night, so I thought I would calculate what Santa’s night would look like!

There are 1.9 billion children in the world, and 31.5% of the world is Christian. Therefore, Santa would have to deliver gifts to 600 million children, and assuming 3.5 children per household, he would deliver to 171 million households. Santa, if he were smart, would travel west so he would have 31 hours to deliver gifts, and would have to travel 133 million miles (assuming .75 miles between households). So, the sleigh would have to travel at 4.3 million mph, or 1,000 miles per second. Faster, in reality, since he would have to include stopping time at each house! The fastest man made vehicle on earth only moves at 27.4 miles per second. For acceleration:

 x=vt+½at²

2.14×10¹¹ m = 1.6×10⁶ m/s (111600 s)+½(111600)²a

a=5.9 m/s²

Additionally, the sleigh would have to decelerate constantly, since it would constantly have to stop at houses.

Furthermore, the weight of the gifts on the sleigh would be enormous.  Assuming each child gets a 5 lb. gift, there would be 3 billion pounds on the sleigh, which is equal to 1.3 x 10¹⁰ N. Each of the 12 reindeer would then have to pull 1.6 x 10⁹ N, not even including the mass of the sleigh itself and the overweight Santa Claus. And I don’t even know the physics behind a man trying to squeeze down a chimney!

Overall, Santa and his reindeer would definitely crash and burn without a little bit of magic.