# Thread: Maximum Velocity in a vacuum

1. Hello. can anyone help me with this? i'm not sure how to calculate special relativity formulas.

Object A is a 1000KG
Object B applies 100KG of constant force.

A & B is in a vacuum with no other variables of course.

how fast could object A and B go giving the fact that the mass increases the fast it goes? and how long would it take to get to 25, 50 and 75% it's maximum (or generally close to) speed.

Thank you.

2. Originally Posted by Mr LeClair
Hello. can anyone help me with this? i'm not sure how to calculate special relativity formulas.

Object A is a 1000KG
Object B applies 100KG of constant force.

A & B is in a vacuum with no other variables of course.

how fast could object A and B go giving the fact that the mass increases the fast it goes? and how long would it take to get to 25, 50 and 75% it's maximum (or generally close to) speed.

Thank you.
Solve the differential equation:

Since you are in 8-th grade, I doubt that you know how to.

are u certaij this is the right formula?

4. Originally Posted by Mr LeClair

are u certaij this is the right formula?
yes, i am certain

5. what does the d/dt stand for?

6. Originally Posted by Mr LeClair
what does the d/dt stand for?
Derivative with respect to time. You do not have the basics to solve this problem.

7. you seem smart enough to know you're own answer.

are you always so condescending or am i misreading you're approach?

8. it's mass is constant, no derivatives are over time.

9. Originally Posted by Mr LeClair
you seem smart enough to know you're own answer.

are you always so condescending or am i misreading you're approach?
I am simply stating a fact: you do not have the basics to solve this problem. BTW, your grammar is atrocious.

10. well you're as useless as tits on a bull.

11. Originally Posted by Mr LeClair
it's mass is constant, no derivatives are over time.
You need to learn the basics, based on your posts, you clearly do not have them.

12. no.. no i dont. and you dont need to help me with this.. you dont need to reply. but i asked if anyone could. and i got you.

you might know your math and formulas.. but those strong points are apparently overshadowed by aspects of ur poor personality. tho this might just be a bad first impression.

13. Andrew: Answer, help, but don't be rude.

Mr LeClair: Don't be rude back, either.

Now, does the mass increase or does the mass remain constant, over time?

14. thank you so much "speedfreek".

and.. its a 100kg of constant force pushing against something that would weight a 1000kg on earth, but its in the vacuum of space.. without anything holding it back. no gravitational variables or other sources of matter.. im not sure if simple weight without mentioning dimentions and material is enough.

just plain old force pushing on something.. whats the rate of excelleration and how fast could it posibly go. i heard mass increases as it aproaches the speed of light to the point of suposed infinity but yea.

just when does it balace out that a 100kgs of force balances out.

as far as time itself effecting the mass. no it wouldnt effect it in itself (i dont think..?) and wouldnt pick up anything along the way.

geez a hope you can connect the remaining dots if i missed anything. thanx again.

15. So, as you apply the constant force, and the object accelerates, its (relativistic) mass increases, over time. This means, in order to keep accelerating the mass, you need to apply more and more force to try to keep the same acceleration (you cannot keep the same acceleration for ever), or the same amount of force will produce less and less acceleration as you approach the speed of light.

What you will find is that the force (or more accurately the energy) required to accelerate the object to the speed of light is infinite. You can never accelerate a mass to the speed of light. You can put more and more force (or energy) in, but with diminishing returns, which diminish to nothing before you reach the speed of light.

Only mass-less particles can travel at the speed of light.

16. ok so how fast would it go when a 100kg couldnt create any more acceleration?

and how fast is 25, 50 and 75% of that and how long would take to ge to those speeds?

would it take a long a while to calculate that?

17. I refer you to post #2. You'll need to solve that differential equation.

18. Originally Posted by Mr LeClair
ok so how fast would it go when a 100kg couldnt create any more acceleration?

and how fast is 25, 50 and 75% of that and how long would take to ge to those speeds?

would it take a long a while to calculate that?
Unfortunately, 8th-grade maths simply will not suffice.

This is the type of problem that requires a command of calculus. You'll either have to put aside the question, or obtain the necessary schooling. There is no shortcut. Sorry.

19. Originally Posted by Mr LeClair
thank you so much "speedfreek".

and.. its a 100kg of constant force pushing against something that would weight a 1000kg on earth, but its in the vacuum of space.. without anything holding it back. no gravitational variables or other sources of matter.. im not sure if simple weight without mentioning dimentions and material is enough.
First off, If you are using kg as a measure of force, then you are using a system of units that has no named unit for mass. In this system, length, force, and time are fundamental units, but mass is a derived unit. (This is called the gravitational MKS system.) Generally, in physics formulas, we use the absolute MKS system, where length, mass, and time are fundamental units and force is a derived unit. In this system, the unit of force is called a Newton (abbreviated as N) .

In this system, the force pushing on the object would be 980 N and the mass of the object would be 1000kg (in the absolute system, something that weighs 1000kg in the gravitational system, would have a mass of 1000kg, and weight 9800N)

just plain old force pushing on something.. whats the rate of excelleration and how fast could it posibly go. i heard mass increases as it aproaches the speed of light to the point of suposed infinity but yea.

just when does it balace out that a 100kgs of force balances out.

as far as time itself effecting the mass. no it wouldnt effect it in itself (i dont think..?) and wouldnt pick up anything along the way.

geez a hope you can connect the remaining dots if i missed anything. thanx again.
The acceleration rate (as measured by someone not accelerating with the object) would start off at 0.98 m/s^2 And would fall off after that. Not noticeably at first, it would need to get up to a appreciable faction of the speed of light before you really start to see much of a decline (at 10% of the speed of light it will have decreased to 9.75 m/s^2).

By the time it reaches 50% of the speed of light, it will be down to 8.49 m/s^2. At 90% it will be down to 4.27 m/s^2 and at 99% it will be 1.38 m/s^2. Notice how much it dropped between 90% and 99% compared to how much it dropped between 10% and 50% of the speed of light. At 99.9% it will be down to 0.438 m/s^2, and at 99.99% it will be 0.139 m/s^2. It will never actually stop accelerating, but neither will its speed ever reach the speed of light. It just gets closer and closer to it but never quite getting there. The object's speed is "asymptotic" in nature; It continually approaches a value but never gets there. Think of the fraction 1/x, where x is an ever increasing number. The larger x is, the smaller the fraction and the closer to the value of zero it becomes, but no matter how large you make x, the fraction never equals zero.

So the upshot is that you can keep pushing on the 1000 kg mass with a constant force forever, and it will continue to move faster and faster, but the rate at which it increases speed falls off in such a way that it never can reach the speed of light.

20. thank you so much for that detailled response. better then originally thought. and helps with ly learning curve on the subject. thanx a bunch!

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