/sci/ - Science & Math

[Anonymous No.2323728]

[spoilers]i don't understand science[/spoilers]

if you built a frictionless vehicle and attached a light source to one side of it, would it start moving in the direction opposite the beam due to the force of the photons? Would it move at the speed of light?

Pic unrelated.

[Anonymous No.2323734]

Yes, it would move.
No, it would move really fucking slowly.

[Anonymous No.2323747]

>>2323734
why

>a doutch
hey, YOU'RE a doutch!

[Anonymous No.2323754]

>Trying to use spoiler on /sci/ They don't exist

[Anonymous No.2323756]

>>2323747

[Anonymous No.2323770]

>>2323754
i don't think he was really trying to do it, he put spoilers plural. it's like when people put /thread, they're just saying it.

[Anonymous No.2323812]

>>2323728

Yes, because photons carry momentum.
No, because mass of the vehicle is incredibly large so the "transfer" of momentum will be quite small.

[Anonymous No.2324049]

f = ma

use your logic, photons are massless particles. they do, however, have momentum.

[Anonymous No.2324079]

yes.no.

[MusicPiggy !!iMBB9yBnJYG No.2324087]

Wouldn't it just be accelerating in the opposite direction very slowly? After a given amount of time, would it eventually move at the speed of light?

[Anonymous No.2324097]

F=ma=dp/dt (p=momentum)

If you're constantly emitting photons aren't you constantly changing momentum aka accelerating?

[Anonymous No.2324115]

>>2323734
It will have constant acceleration, so eventually it will be moving fast relatively to what you consider fast

[Anonymous No.2324128]

>>2324115
Or the battery will run out.

[Anonymous No.2324287]

>>2324087
No, it would never reach the speed of light. Relativity shows that the force required to continue accelerating something at the same rate increases asymptotically as the speed approaches light speed. Don't ask me to prove it because I have no clue how, although you could probably find a proof, at least a mathematical one, with a google search.

[Anonymous No.2324301]

If the speed of light, c, is constant, there is no change in momentum. There is no change in velocity, so no acceleration. Thus, no force; thus, no action-reaction pairs. So no OP, it wouldn't.

[Anonymous No.2324304]

>>2324287
Actually I can show kind of why.
The equation for the mass of a body moving at relativistic speed is \left M=\frac{m}{\sqrt{1-\frac{v^2}{c^2}}} \right
Where the little m is the bodies rest mass, v is its velocity and c is the speed of light.

It is obvious from that equation that the velocity can never equal that of light. If you want a proof of that equation, however, you're on your own.

[Anonymous No.2324314]

>>2324301
So you take a photon, you eject it from something attached to your vehicle. The photon has momentum, and the opposite and equivalent amount of momentum gets put into your vehicle. A constant stream of photons provides a constant change in momentum (constant force).

[Anonymous No.2324338]

>>2324314
Okay, fine, then see it in this way: the photons have an infinitesimal amount of mass, yet non-zero, and therefore the opposite and equal force/momentum back on the vehicle would be so small that there would be a virtually unnoticeable change in the vehicle's momentum/force.

Anyway, your statement still doesn't really hold up. It's a constant velocity, there is no acceleration. No constant force.

[Anonymous No.2324343]

>>2324287
As you speed something up you increase it's kinetic energy. This kinetic energy has an equivalent mass (the whole E=mc^2) and so as you speed up you basically get heavier. This has an asymptotic effect as you approach speed of light.

[Anonymous No.2324349]

>>2324338
Photons have no mass. They have a nonzero momentum. And we're already talking about a bullshit scenario (frictionless vehicle) even if it takes a billion years to accelerate to 1m/s it doesn't matter, it's a thought experiment.

[Anonymous No.2324513]

>>2323728

Need more info.Based on what's been given no it won't reach c.