Where to begin with the movie Eraser? There are so many bad examples of physics, but I only have so many words I can type...
So let’s begin with analyzing why dual-wielding 2 railguns would effectively kill you (unless you’re Arnold Schwarzenegger of course).
In the movie, after being fired upon for what seems like ages, Arnold's character picks up 2 railguns and decides to give the enemy a taste of their own medicine. He then goes on a firing spree, spraying bullets at near the speed of light at his enemies. Since the bullet is traveling near the speed of light, I approximated 95% of the value for the speed of light which resulted in 2.85x108 m/s. Since I am going to examine the physics of the momentum from the guns, I will be using the conservation of momentum equation below.
mavaf + mbvbf = mavai + mbvbi
Here are the variables:
ma = Mass of Arnold = 115 kg
mb = Mass of bullet = 0.100 kg
vai = Arnold’s initial velocity = 0 m/s
vbi = Bullet’s initial velocity = 0 m/s
vbf = Bullet’s final velocity = 2.85x108 m/s
vaf = Arnold’s final velocity = ?
Cancelling all the variables that equal zero gives us this equation which we then solve for vaf.
Vaf = -mbvbf
vaf = -(0.1)(2.85x108)
Vaf = -248000 m/s
This means that after firing the railgun, Arnold would have been sent back at a speed of 248,000 meters per second. But this is for only 1 railgun. In the scene, Arnold is dual wielding a pair of railguns. This effectively doubles the speed at which he would be sent back, meaning that had he fired both railguns at the exact same time, he would have been sent back at 496,000 meters per second. But as we all know, with muscles like his, Arnold would have resisted all that force and most likely have pushed the guns forward while firing them...
Now, to examine how fast the villain would have flown back had Arnold hit him with a bullet fired from a railgun. We will be using the same equation as before with the same variables except for the variables dealing with Arnold, we will switch them out with variables relating the villain like, as we see below.
mv = Mass of villain = 90 kg
vvi = villain’s initial velocity = 0 m/s
vvf = Villain’s final velocity = ?
We also need to assume the bullet stays with the villain, so the final velocity of both the bullet and the villain will be the same. This gives us the resulting equation for us to solve for vf.
vf = mbvbi
vf = (0.1)(2.85x108)
(90) + (0.1)
vf = 316000 m/s
This means that the villain, after being shot with a railgun, would fly back at a speed of 316,000 meters per second, and since he is not the main character, he can actually die in the movie. Even though we haven’t talked about force in class yet, I believe being shot with a bullet fired at that speed and having you fly back at that speed would have a high enough force to kill you, so long as you’re not Arnold Schwarzenegger.