Eraser

In my opinion, Eraser is a typical action movie, and along with being a typical action movie, it has action movie physics, which don't always line up with the truth. In Eraser, the major plot device is a handheld railgun that shoots aluminum close to the speed of light (yes, I know this is ridiculous but just roll with it) and it is shot like any standard gun, but whoever is shot goes flying back.

c = Speed of Light = 2.998*10^8 m/s
vib = Initial Velocity of Bullet = approx. 2.5*10^8 m/s
vfb = Final Velocity of Bullet = 0 m/s
mb = Mass of Bullet = approx. 5.0 g
vit = Initial Velocity of Thug = 0 m/s
vft = Final Velocity of Thug = ? m/s
mt = Mass of Thug = approx. 80 kg

for the purposes of this problem assume all momentum is conserved in a perfectly elastic collision

If all of the momentum had been conserved (which it hadn't, because if you check the clip, the bullets don't slow down after hitting the thugs, but if it stayed at the same velocity, we wouldn't have any physics problems to solve and the thugs would have just stayed in place) the thug would've been thrown back at 160,000 m/s, but if ALL of the momentum had been conserved , Arnold would have been shot back just as fast, killing him as well.

I rate the physics in Eraser XP

Comments

  1. I think you could have been a bit more clear for your readers about why Arnold would have been shot back. You mention that this is true if "ALL of the momentum had been conserved," but momentum is always conserved in isolated systems. So whatever momentum the bullet and bad guy carried in the positive direction, Arnold and the gun would have had to carry the same momentum in the opposite direction since the initial momentum of the system was zero.

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