Eraser

Eraser, much like many 90's action films, is jam packed with corny dialogue, over the top fight sequences and of course Arnold Schwarzenegger. The movie is enjoyable to an extent if you're able to ignore the obviously horrible physics regarding the movies main subject, the rail gun. The rail gun in the movie is a weapon designed to shoot small aluminum bullets at the speed of light. The concept of the weapon is already extraordinary but the physics applied are even more crazy.

Here in the movie Arnold finally gets a hold of the rail gun and has a blast. In the scene we see Arnold rapidly fire the rail guns subsequently sending the bad guys flying while we see he takes little to know recoil. The fundamental problem here is if the bullets were to some how launch the bad guys, the force from firing the gun would also launch Arnold in the opposite direction. Applying the law of conservation of momentum we can calculate the velocity at which Arnold would go flying backwards. In order to solve this problem we need to list all the variables before plugging them into the equation for the conservation of momentum...

MaVfa + MbVfb = MaVia + MbVib 

Ma and Mb being the mass of Arnold and the bullet as well as Vf and Vi being the final and initial velocity of Arnold and the bullet respectively. After some brief research we know Arnold weighs about 113 kg and the bullet about .007kg considering the average aluminum bullet is about .262 ounces. We know visually from the scene Arnold and the bullets initial velocity are 0 because Arnold is not moving and the bullet hasn't been fired. The movie also says the gun fires the bullet at the speed of light making the bullets final velocity 3.0 x 10^8 m/s.
Now plugging this information into the equation and solving for Arnold's final velocity we get....

Vfa = -.007kg(3 x 10^8 m/s) / 113kg = -18,584.07 m/s  

Meaning after firing the rail gun Arnold would go flying at -18,584.07 m/s backwards, if not obliterated upon pulling the trigger. Now multiply that by the amount of times Arnold fired the weapon and you get an absurd number to correlate with some absurd movie physics.

Using the ISMP ranking system I would give this movie a PGP-13 because as a naive child I would have for sure believed the physics in the movie without batting an eye.

         

Comments

  1. Prof. Chris FragileSeptember 26, 2019 at 9:44 AM

    Nicely done. A few typos, but I like that you went through a calculation to show how absurd the final answer would be.

    ReplyDelete

Post a Comment

Popular posts from this blog

Armageddon

Image
The movie Armageddon is about a scenario where an asteroid is plummeting towards earth and NASA has to think up a quick plan to save the human race. This brings up the question of what plans does NASA have for a real world Armageddon situation. NASA in fact just recently in April of 2019 created an asteroid impact exercise to help prepare key decision makers on the "what if?" scenario. The participants discussed economical and human consequences of the impact on a densely populated area like New York City. The main point of the exercise being how they would change the trajectory of the asteroid. On the second day of the five day exercise the NASA team details how they would use three Kinetic Impactors (KIs) to deflect the asteroid causing it to bypass earth. Kinetic Impactors are large spacecrafts that are sent into the path of an object coming towards earth in order to make contact and hopefully knock it off course. In the exercise the first Kinetic Imp
Read more

Weapons of Mass Destruction

Image
The creation of weapons of mass destruction has been a troubling moral concept since the creation of the first atomic bombs in the 1940's. Personally, I believe the construction and research of these weapons is morally wrong. I think the creation of extremely powerful weapons that pose a threat to humanity as whole is objectively bad from a positive moral stand point. The creation of weapons of this nature bring up many moral quandaries like, why or when would a weapon of this magnitude be a viable option in world conflicts. Although the actual construction of the weapons poses no direct threat its the implication and use of the weapons in a foul way that is troubling. We see this directly in history after the drop of the two bombs on Nagasaki and Hiroshima, where countless innocent people lost their lives and the world was then sent into a frenzy of creating nuclear warheads in fear of their countries safety.   
Read more

The Martian and Philip Plait's "Bad Astronomy"

Image
In chapter 24 of Bad Astronomy, Philip Plait breaks down his top ten bad examples of astronomy in movies and TV.  1. Plait's first example is one of the most common concepts done wrong in Hollywood movies. This mistake is that their is sound in space. In order for sound to travel it has to have something to go through. On earth we are able to hear because the vibrations that produce sound are transferred from the atoms in the air to our ears. So in space, because their is nothing for the vibrations to be transferred to, no sound would be able to be perceived in space. We see this violated in The Martian when Mark Watney (Matt Damon) is blasting out of Mars' atmosphere. 2. Example 2 doesn't apply to The Martian because it deals with the perception of asteroid fields in movies being extremely dense and that isn't a problem that appears in the movie. 3. In this example Plait uses the example of space crafts making sharp turns in order to redirect the trajector
Read more