Speed and mass question

[YT2095]

the faster you go the more massive you become, the more masive you become the more energy is needed to accelerate you. and so it continues to such a point that it`s impossible to travel any faster and certainly impossible to reach light speed.

with one exception, the Photon, that may travel at light speed because it has no mass.

that`s roughly a summary of the posts so far as I understand them

[aommaster]

ooohh, so THAT'S why EM waves travel at the speed of light, they have no mass!

That means, if i am travelling at a speed of 10 km/h in a car, will i have a greater mass than that if i was standing still? Should be, or I'm confused!

[JaKiri]

Ever so slightly.

[aommaster]

ok. Thanx, that sorts a few things out!

Now, WHY does the mass change when ur speed changes? That is the question!

[blike]

Haha, you might want to check out brian green's book "The Elegant Universe". He does a fair job of explaining all the implications and effects of relativity to us laymen.

[aommaster]

oh ok! But i dunno if i get it over here!

[blike]

From what I understand, its based on conservation of momentum. See this page:

 

http://galileoandeinstein.physics.virginia.edu/lectures/mass_increase.html

[YT2095]

because it exerts force of acceleration upon you (a bit like gravity but that`s passive in this instance)

if you weight 100 pounds on earth (1 G) then you accelerate to 2 Gs you`de effectively have twice the mass. 7 G`s or more, you`de become so massive your heart wouldn`t be able to pump against the "Gravity" your blood would be more massive (I hesitate to use the term, "Weigh more")

infact in this instance it would be made to artificialy "weigh more" and it would probably kill you. a bit like how you can get thrown back in your seat sitting on a fast plane at take off.

the same applies to little particles too, except for photons that have no mass to start with

 

I Think I`ve got that right?

[aommaster]

hmmm... looks like its correct It makes sense to me! Thanx alot YT

[blike]

Nooo, thats only acceleration. What happens when you stop accelerating? Let's say you are travelling .99 the speed of light, but there is no acceleration. If you were in the middle of black, gravityless space (hypothetically), you wouldn't even know you were moving.

[aommaster]

one more thing to add, look at ur post and blike's post! SAME TIME!!!

[aommaster]

i thought u would actually loose mass, won't u?

[JaKiri]

:up:

[blike]

No, you're confusing acceleration with velocity.

[aommaster]

oh yeah! sorry, if u stop accelerating, won't ur mass be back to normal? Even though u are moving, there is no extra force exerted on u! Well, that's what i think! Ask a pro here!

[YT2095]

I possibly am, but it`s about the only way I could think of describing it. for this instance though it seemed a simple but working example, lemme try again:

 

think of dropping a bullet on a lead plate from 1 meter high, it`ll leave a hypothetical dent of say 1mm, now double it`s velocity and you`ll get a 2mm deep dent.

or you could keep it at the 1 meter hight and double it`s weight and still get the 2mm dent.

 

so velocity and weight are interchangable (ignoring airodynamics etc...)

again, it`s only a simple explaination, but what ya expect, I`m a Chemist primarily

[blike]

What you're talking about is the force due to acceleration. That is not the same thing as mass.

 

Let's say an astronaut experiences 4Gs on his ride in the space shuttle. That doesn't mean his mass has increased four times. It means the acceleration has increased to four times the earth's acceleration (9.8m/s^2). F=ma. As you can see, the force his body places on his seat will increase, but his invariant mass has not increased, only the acceleration.

 

That is different from relativisitic mass, which increases with velocity, not acceleration. Read the link I sent you regarding conservation of momentum.

[YT2095]

what link dude? it`s win 98 here doesn`t show em all sadly

 

I do understand the principle a little, I just lack the words I guess.

the way I see it is a bit like critical mass in a nuke, both componants are sub critical, and just touching them together to make a near critical mass would at best create a meltdown, but surrounded by conventional explosives the mass can be made super critical by virtue of the velocity on impact (hence the need for exact prescision and alignment as well as timing.

a similar principal applies to bullets and shaped charges.

velocity and mass go hand in hand.

I just find it difficult to word it

[blike]

YT2095 said in post # :

think of dropping a bullet on a lead plate from 1 meter high, it`ll leave a hypothetical dent of say 1mm, now double it`s velocity and you`ll get a 2mm deep dent.

or you could keep it at the 1 meter hight and double it`s weight and still get the 2mm dent.

 

so velocity and weight are interchangable (ignoring airodynamics etc...)

again, it`s only a simple explaination, but what ya expect, I`m a Chemist primarily

 

Weight is a measure of force and acceleration, but it is not the same thing as mass. What you're describing is a difference in kinetic energy, due to velocity and mass. However, the mass is not the variable factor in your situation, only the velocity.

 

For example, lets say we could hypothetically detect the bullets mass (not weight or force) while its falling by calculation its gravitational affects on nearby objects. According to Newton, the actual MASS of the object is independant of its speed. Even fired from a gun, according to newton's equations, the mass of the object would remain unchanged. Yes, the force, acceleration, and kinetic energy of the bullet would change, but the mass would not.

 

Einstein says the MASS changes with velocity.

 

 

Let's calculate the inertial mass of the space shuttle orbiting the earth.

 

An orbiting space shuttle (right before re-entry) typically weighs 104326.2451kg and orbits at a speed of 27875 km/h.

 

Thus, the velocity is 464583.33 m/s

 

Using the equation:

 

m(v) = 104326.2451kg / sqrt(1- (464583.33^2 / 299792458^2))

 

m(v) = 104326.4956kg

 

Thus, the mass of the space shuttle is increased by its velocity by 250.5g or .0002401%.

 

As you can see, it takes a lot of speed to increase the mass by any significant factor.

[YT2095]

well I kinda understood the punchline

 

what of something that moves at 22 miles per second, say a 1 gram projectile, what would your calcs show for that as mass increase?

 

(my maths sucks, I`de just like a basic model at the end of the day)

 

cheerz

[JaKiri]

It is NOTHING TO DO WITH FORCE.

 

It's you velocity relative to the rest frame that matters.

[YT2095]

and so I lay out 22 miles of detacord (PETN based), are you telling me that even at those velocities that there would be no mass increase along its length?

[JaKiri]

YT2095 said in post # :

and so I lay out 22 miles of detacord (PETN based), are you telling me that even at those velocities that there would be no mass increase along its length?

 

What?

 

I was replying to post 'think of dropping a bullet on a lead plate from 1 meter high, it`ll leave a hypothetical dent of say 1mm, now double it`s velocity and you`ll get a 2mm deep dent.

or you could keep it at the 1 meter hight and double it`s weight and still get the 2mm dent.' that one.

 

As to the 22 miles per second one, you'd get a mass increase of 0.0000007%.

[YT2095]

can you explain why then the 2 semi critical masses in an atomic weapon have to be slammed together at such a huge velocity if it makes such a small to insignificant difference?

surely a simple spring mechanism making them touch at the correct time for detonation would be sufficient and there would be no need whatsoever for the use of conventional explosives or such carefull measurements and timing.

treat this as just an atomic weapon, forget nuclear or hydrogen bombs that use this method as a detonator, consider just the detonator, for maybe a 100 kiloton yeild.

[blike]

Somewhat offtopic, but the speed with which they're slammed doesn't increase their mass. Its the fact that their summed masses bring them to a critical mass. I'd imagine they're "slammed" together in order to provide some extra energy and get the party started at a devastating rate.