How fast would a bullet weighing .005 Kg needs to be traveling to bring a 20,000 Kg tractor trailer moving at 24 m/s to rest? (assume the bullet sticks to the truck) Could this be possible if the maximum speed possible is 3 x 10^8 m/s?
2006-11-14 13:58:10 · 4 answers · asked by mike p 2 in Science & Mathematics ➔ Physics
What a terrible (or great) question!
Any object with mass travelling at 3x10^8m/s (the speed of light) has infinite energy. Not only would it stop the tractor, it would utterly destroy it, and the rest of the universe. Note that this can not be shown with the Newtonian kinetic energy formula, you have to use Einstienian mechanics to prove this (http://en.wikipedia.org/wiki/Kinetic_energy)
But that's only part of the question. Set the momentum (p) of the tractor equal to that of the bulet.
(2x10^4kg)(24m/s)=(5x10^-3kg)v
v=9.6x10^7 m/s
That's a good fraction (~ 1/3) of the speed of light, so if you're in a university level physics class, you'll need to use Einstien to get a more acurate number. But either way that's pretty close.
Normally, I don't give out actual numerical answers, but I needed the number in this case to make the point regarding relativistic velocities.
2006-11-14 14:15:35 · answer #1 · answered by Michael E 2 · 0⤊ 0⤋
the wear performed through both bullet and punch is the ingredient of two issues a million. the momentum with which the effect has been made. Momentum is the made from the speed and the mass of the article. the mass of the bullet is really a lot less while its speed is really severe. on the different hand even as punching the speed of the fist is a lot less although the mass (entire body helps it in spite of the actuality that) is severe. 2. the element of effect on which the effect has been made. the section on which bullet hits is really small as compared to the punch. The bullet is going in to the body, because the rigidity created is only too severe, so bullet honestly pierces the body. rigidity = rigidity / section besides the bullet is deadly because it causes extra damage to the gentle inner organs and leads to bleeding.
2016-11-24 20:13:36 · answer #2 · answered by ? 4 · 0⤊ 0⤋
pretty fascinating question.
The conservation of momentum can be solved numerically for the relativistic case. v= 9.14E-7 m/s, so not that far off from the Newtonian answer. The reason is that the Lorenz transform isn't really as strong as it looks when v isn't anywhere near 0.9*c.
http://en.wikipedia.org/wiki/Momentum#Momentum_in_relativistic_mechanics
The bullet would need to be 1/10 the mass specified to get a factor of 4 difference between Newtonian and relativistic scenarios.
2006-11-14 17:56:09 · answer #3 · answered by arbiter007 6 · 0⤊ 0⤋
I don't think the bullet would have enough mass to stop the tractor at any speed.
2006-11-14 14:01:01 · answer #4 · answered by Chris J 6 · 0⤊ 1⤋