Sunday, September 27, 2015

The Physics of The Flash

We all know The Flash can run super fast up the sides of buildings, across water, and able to catch bullets. As far as going up the side of a building, we know that as one rises, they slow down due to gravity until they reach a height where the final speed is zero. As he approaches the side of a building, as long as he maintains a speed grater than v^2=(2gh), he should be able to make it to the top of the building while still following the laws of physics.


According to Newton's 3rd Law, every action has an equal and opposite reaction. In order to walk, the ground must exert the same amount of force you put on it and you must have friction. The Flash must have friction in order to go super fast. One of the supervillans he must fight is Captain Cold, who shoots a layer of ice in front of him, rendering him unable to get any friction on the ground, and unable to use his super speed. 

In order to walk across water, the water must move out of your way. If a liquid has a higher viscosity, it requires more energy to move it out of the way. The Flash is able to run faster than it takes the water molecules to displace and move out of the way, so therefore he can keep moving on top of them. The water acts more like a solid than a liquid at these speeds, you can see this by slapping a pool of water really quickly. 



For The Flash to catch bullets, he would need to speed up to match the bullet's velocity so the net speed between him and the bullet is zero. He can then easily pick the bullet out of the air and save the innocent bystanders. 

Kakalios, James. "Flash Facts-Friction, Drag, and Sound." The Physics of Superheroes. N.p.: Gotham, 2006. 57-68. Print.

Sunday, September 20, 2015

Armageddon

NASA has proposed many different possible ways of deflecting an asteroid from earth. There are two ways to do this, nuclear and non-nuclear.

If NASA were to use nuclear power, there are four effective ways to try to get the asteroid off course. A surface explosion, a delayed surface explosion, a subsurface explosion, and an explosion where the bomb does not touch the asteroid.

The best option for a non-nuclear defense plan is a series of kinetic impacts. This is basically just ramming things into the asteroid until it's path is changed to avoid hitting earth. Other ways are using a laser or a huge mirror to focus energy on the surface of the asteroid to try to break off pieces of it.

My favorite plan that NASA came up with was the subsurface nuclear explosions, because that is what they tried to do in the movie. Except NASA would use it to try to move the asteroid off course instead of breaking it in half, like what they did in the movie. Nuclear weapons are the only thing that would provide the amount of energy needed to divert an asteroid of that size. NASA proposed the Hypervelocity Asteroid Intercept Vehicle (HAIV). This would create a crater on the surface of the asteroid where the nuclear bomb would be detonated after.

Using this, they would be able to neutralize an asteroid that is 1,000 feet across if they know about it at least 30 days in advance.
This would create enough energy to hopefully change the asteroid's velocity, pushing it away from the earth. You would need megatons of energy in order to achieve this.

Unfortunately, due to Article IV of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, detonating nuclear weapons in space is illegal. But maybe NASA could try and change some minds if the fate of the planet was in jeopardy. 

Sunday, September 13, 2015

Eraser

Arnold Schwarzenegger is the protagonist of an action film where he erases people and gives them new identities. The main weapon of choice is a rail gun. The physics of a rain gun is pretty complex and the movie follows these physics very poorly. When Arnold shoots the rail gun, he would have had to flown backwards when the bullet leaves the gun.

Ma= Arnold's Mass
Mb= Bullet's Mass
Vai= Initial velocity of Arnold
Vbi= Initial velocity of the bullet
Vaf= Arnold's final velocity
Vbf= Bullet's final velocity



Arnold would have had to have flown backwards at 30,000 meters per second.

When it comes to how fast the victim would have flown backwards, the movie is wrong again. Assuming the bullet stuck in the victim, Vfv=Vfb=Vf, the movie's physics is all inaccurate. 

Mv=Victim's mass
Mb= Mass of the bullet
Vfv= Final velocity of the victim 
Vfb= Final velocity of the bullet
Vib= Initial velocity of the bullet
Viv= Initial velocity of the victim



The victim would have had to been flying backwards at 37,000 meters per second. 

Sunday, September 6, 2015

Mission Impossible III


In Mission Impossible III, Tom Cruise has to retrieve The Rabbit's Foot from the bad guy in order to save his wife's life. In one of the many climatic scenes, he has to swing from a building that is 226 meters tall to the building the Rabbit's foot is located in, which is 162 meters tall. The two buildings are 47.55 meters apart. It took him approximately 20 seconds from the time he left the top of the building to the time he released himself from the rope onto the second building. Would he have been going fast enough just from jumping off the building to make the swing to the other building? 

My second question comes from the same scene. When Tom Cruise is jumping off the building and the rope runs out and becomes taut, would that have broken his spine? It takes more than 3000 newtons to fracture the cervical spine and become paralyzed. Tom Cruise weighs approximately 67 kg. If we ignore air resistance, his acceleration would have been 9.81 m/s^2.

F=m*a
F=(67 kg)(9.81 m/s^2)
F= 660 newtons
The fall would not have broken his spine, leaving him able to save the day and his wife.


In another climatic scene, Tom Cruise is rescuing another agent and throws a grenade which I assume is magnetic, as it is pulled towards a metal pole and sticks. It takes less than two seconds to throw it about 6 meters. My question is why did it go straight to the pole after throwing it in a curve and in a mostly metal warehouse?