View Poll Results: How fast?
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- 23. You may not vote on this poll
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Don't know
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faster than parksie
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0.2c
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0.38c
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0.42c
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0.5c
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very fast
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c
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slow as kedaman
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other
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Apr 10th, 2001, 05:32 AM
#1
Thread Starter
transcendental analytic
spaceship A travelling at 0.6c is chasing another spaceship B travelling at 0.8c, which is of course trying to get away. Now spaceship A fires a missile at spaceship B, what minimum speed does the missile need (relatively to A) to have to hit B?
Use  
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
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Apr 10th, 2001, 05:51 AM
#2
Frenzied Member
couldn't it be anything greater than 0 (considering that the missile is already moving forward due to the shiips motion)? And by the way...what is c?
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Apr 10th, 2001, 05:55 AM
#3
Thread Starter
transcendental analytic
yeah sorry, i didn't mention, c is the speed of light: 300 000 km/s
and for all those poll options, i meant "faster than"
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
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Apr 10th, 2001, 05:59 AM
#4
0.800000000000000000000000000000000000000000000000000000000000000000000000000000000..........etc etc......0001c
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Apr 10th, 2001, 06:06 AM
#5
Thread Starter
transcendental analytic
isn't it
0.800000000000000000000000000000000000000000000000000000000000000000000000000000000..........etc etc......00001c
chenko?
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
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Apr 10th, 2001, 06:21 AM
#6
well anything above 0.8c is correct, the minumun is 0.8 then 0 for infinity and a 1 on the end.....
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Apr 10th, 2001, 06:25 AM
#7
Monday Morning Lunatic
Hehe so who else voted for me?
I refuse to tie my hands behind my back and hear somebody say "Bend Over, Boy, Because You Have It Coming To You".
-- Linus Torvalds
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Apr 10th, 2001, 06:25 AM
#8
Thread Starter
transcendental analytic
relatively to A, that is the velocity at which the missile travels from A
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
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Apr 10th, 2001, 06:27 AM
#9
Anything is faster than you so it was a logical answer!
Kedaman: So I got It right then? 
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Apr 10th, 2001, 06:35 AM
#10
Thread Starter
transcendental analytic
look at this:
this is relatively to start point, the point where parksie travels from at 0.6c
[parksie]>........[chenko]>
......[parksie]>................[chenko]>
............[parksie]>..*....................[chenko]>
..................[parksie]>.....*.........................[chenko]>
........................[parksie]>........*..............................[chenko]>
this is relatively to A, in this case parksie
[parksie]>........[chenko]>
[parksie]>................[chenko]>
[parksie]>..*....................[chenko]>
[parksie]>.....*.........................[chenko]>
[parksie]>........*..............................[chenko]>
now looking at this, what speed does * need to travel to catch up chenko.
so that it will look like this:
* *. *
*...* .*
. *** .*
*...*.*
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
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Apr 10th, 2001, 06:51 AM
#11
PowerPoster
After the missile left Parksie It does not matter how fast Parksie is, so I'd say just more than the difference between the Parksie and Cenki and thats 0.2c - I'm sure there's something wrong with that so I vote for "very fast" though
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Apr 10th, 2001, 07:26 AM
#12
It dosent matter how fast parksie is when it leave him.
Im still sure its just above 0.8c
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Apr 10th, 2001, 07:33 AM
#13
Thread Starter
transcendental analytic
try that chenko and jump out of the car when it's travelling at 90km/h
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
-
Apr 10th, 2001, 08:19 AM
#14
Frenzied Member
Okay, this is smelling like a trick question. Why is the answer not >.2c?
Travis, Kung Foo Journeyman
As always, RTFM.
WWW Standards: HTML 4.01, CSS Level 2, ECMA 262 Bindings to DOM Level 1, JavaScript 1.3 Guide and Reference
Perl: Learn Perl, Llama, Camel, Cookbook, Perl Monks, Perl Mongers, O'Reilly's Perl.com, ActiveState, CPAN, TPJ, and use Perl;
YBMS, but Mozilla doesn't.
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Apr 10th, 2001, 08:23 AM
#15
Thread Starter
transcendental analytic
yep, but i'm waiting for a smartass to show up and tell me
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
-
Apr 10th, 2001, 08:56 AM
#16
Originally posted by kedaman
try that chenko and jump out of the car when it's travelling at 90km/h
Yea I might fall at near enough where I left the car, but If a missile was fired, It would be forced to accelerate, we arnt really taking speed into account now are we?
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Apr 10th, 2001, 08:58 AM
#17
Ok I have it
Spaceship B runs out of fuel, and the missle can travel at any speed above 0 to hit it!
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Apr 10th, 2001, 09:09 AM
#18
Thread Starter
transcendental analytic
Spaceship B, doesn't happen to have any fuel, it still goes at 0.8c because there's nothing stopping it.
suppose that the missile have enough fuel to catch up Spaceship B
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
-
Apr 10th, 2001, 09:44 AM
#19
Fanatic Member
kedaman, you naughty boy. You KNOW that as velocities approach the speed of light they are no longer additive.
Chenko, close but no cigar, hehehehe
Cheers,
P.
Not nearly so tired now...
Haven't been around much so be gentle...
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Apr 10th, 2001, 09:49 AM
#20
Frenzied Member
I voted. I'm still lost, but I voted.
Travis, Kung Foo Journeyman
As always, RTFM.
WWW Standards: HTML 4.01, CSS Level 2, ECMA 262 Bindings to DOM Level 1, JavaScript 1.3 Guide and Reference
Perl: Learn Perl, Llama, Camel, Cookbook, Perl Monks, Perl Mongers, O'Reilly's Perl.com, ActiveState, CPAN, TPJ, and use Perl;
YBMS, but Mozilla doesn't.
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Apr 10th, 2001, 10:04 AM
#21
Addicted Member
Answer is 0.38 C according to Principle of Relativity
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Apr 10th, 2001, 10:05 AM
#22
Frenzied Member
As a side bar...
if you started timers on both ships and the missile at time of launch and measured time 'til impact, you would get three different readings. All of these readings would also be short of the reading taken by a "stationary" observer.
*shrug* Fun with time dilation.
Travis, Kung Foo Journeyman
As always, RTFM.
WWW Standards: HTML 4.01, CSS Level 2, ECMA 262 Bindings to DOM Level 1, JavaScript 1.3 Guide and Reference
Perl: Learn Perl, Llama, Camel, Cookbook, Perl Monks, Perl Mongers, O'Reilly's Perl.com, ActiveState, CPAN, TPJ, and use Perl;
YBMS, but Mozilla doesn't.
-
Apr 10th, 2001, 10:06 AM
#23
Frenzied Member
Originally posted by Active
Answer is 0.38 C according to Principle of Relativity
This one you will have to explain.
Travis, Kung Foo Journeyman
As always, RTFM.
WWW Standards: HTML 4.01, CSS Level 2, ECMA 262 Bindings to DOM Level 1, JavaScript 1.3 Guide and Reference
Perl: Learn Perl, Llama, Camel, Cookbook, Perl Monks, Perl Mongers, O'Reilly's Perl.com, ActiveState, CPAN, TPJ, and use Perl;
YBMS, but Mozilla doesn't.
-
Apr 10th, 2001, 10:15 AM
#24
Addicted Member
There are Three Inertial Frames in the description,
We the observer is in the Third frame.
According to our Measurments
A is Moving at 0.6c
B is moving at 0.8c
The minimum speed required for a missile from A to
hit B will be the Speed of B relative to A.
If A is moving with velocity u relative to observer and B is moving with velocity w relative to observer then the velocity of B relative to A is given by,
v = (w - u)/(1 - wu/c2)
Using this formula....
v = (0.8c - 0.6C)/(1-(0.8*0.6))
v = 0.2 C / 0.52
v = 0.3846 C
--
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Apr 10th, 2001, 10:16 AM
#25
Thread Starter
transcendental analytic
ok now that you got it
getting v from this formula, you get 0.38c
0.6c+v
__________
1+0.6cv/c^2
i suppose you did this Active
i'm running out of time though, i have another relativistic problem including an angle, and i'm not smart enough to solve it:
A light beam travels at theta' to the x' axis of frame S' which moves at velocity v in the +x direction of frame S. If theta is the angle measured to the x axis, show that:
cos theta =
cos theta' + Beta
______________
1+Beta cos theta'
where Beta = v/c
as a hint it says: Use the Lorentz transformation and note that cos theta = dx/(cdt).
(from Harris Benson/University Physics 39-Problem 7.)
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
-
Apr 10th, 2001, 10:19 AM
#26
Thread Starter
transcendental analytic
slow as usual (me)
i'm really sorry to get your attention like this but i thought you might help me with this problem
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
-
Apr 10th, 2001, 10:25 AM
#27
Frenzied Member
Originally posted by Active
There are Three Inertial Frames in the description,
We the observer is in the Third frame.
According to our Measurments
A is Moving at 0.6c
B is moving at 0.8c
The minimum speed required for a missile from A to
hit B will be the Speed of B relative to A.
If A is moving with velocity u relative to observer and B is moving with velocity w relative to observer then the velocity of B relative to A is given by,
v = (w - u)/(1 - wu/c2)
Using this formula....
v = (0.8c - 0.6C)/(1-(0.8*0.6))
v = 0.2 C / 0.52
v = 0.3846 C
--
Okay, what about the universe causes this to be true? For this to rest well with my soul (humor intended), I have to assume that this is true for terrestrial speeds like 60mph (or 100kph). Is it? If not, why not?
Travis, Kung Foo Journeyman
As always, RTFM.
WWW Standards: HTML 4.01, CSS Level 2, ECMA 262 Bindings to DOM Level 1, JavaScript 1.3 Guide and Reference
Perl: Learn Perl, Llama, Camel, Cookbook, Perl Monks, Perl Mongers, O'Reilly's Perl.com, ActiveState, CPAN, TPJ, and use Perl;
YBMS, but Mozilla doesn't.
-
Apr 10th, 2001, 10:34 AM
#28
Addicted Member
Well..I have to admit there is a flaw in my argument
The minimum speed required for a missile from A to hit B will be the Speed of B relative to A.
It should be atleast more than that ...otherwise it would
never reach B
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Apr 10th, 2001, 11:31 AM
#29
Thread Starter
transcendental analytic
yeah it's a bit hard to evaluate the answer, but you can get close, i don't like that kind of excercises. I guess you have no luck with the one i posted next?
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
-
Apr 10th, 2001, 12:11 PM
#30
Addicted Member
Well I have to say...Gimme some more time..
BTW ...on the Question of CyberThug..
for this to rest well with my soul (humor intended), I have to assume that this is true for terrestrial speeds like 60mph (or 100kph). Is it? If not, why not?
Well... 100kph is 27.778m/s while c is 3x10^8 m/s
that means your 100kph vehicle is 9.259x10^-8 C
Now f we measure two vehicles moving at 30 m/sec
and 35m/sec . they will be like 1 x 10^-7 and 1.16 x 10^-7.
Without relativity we say B is moving at 5m/sec relative to A
Using the above formula again we get the same
because since the two values are really small their
products will be further small.
There fore... the denominator will be 1- very small value...
which is almost equal to 1
So we observe no bigger changes.
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Apr 10th, 2001, 12:24 PM
#31
Thread Starter
transcendental analytic
thanks for your time i guess youre not travelling close to c relatively to me so you might get it solved in 13,5 hours
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
-
Apr 11th, 2001, 03:52 AM
#32
Thread Starter
transcendental analytic
No complex solution here either.
a photon travelling at C in direction theta' in a reference system S' which moves with a speed v in direction x+ in reference system S. And i need to get the angle theta in reference system S. the issue is again relativistic addition, y and z components in the systems are the same, x varies, so we need to get the Vx' component tranlated from S' to S.
Vx' is cos(theta')c and thefore
Vx=
cos(theta')c+v
__________________
1+cos(theta')c*v/c^2
now since we know that c does not vary in any reference system:
cos(theta)=Vx/c=
cos (theta') + v/c
______________
1+cos (theta')*v/c
some basic knowledge of vector calculus and relativistic addition
simple.. eh?
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
-
Apr 11th, 2001, 06:15 AM
#33
Addicted Member
y and z components in the systems are the same
I failed to think like that..since the question doesn't say
like that .... hehehe.... 
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Apr 11th, 2001, 07:15 AM
#34
Thread Starter
transcendental analytic
yeah well it's a bit unclear, but "moves in x+ direction of Frame S" should be understandable
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
-
Apr 11th, 2001, 07:18 AM
#35
PowerPoster
AHA!!!
It wasn't specified that spaceship A was chasing spaceship B in a linear fashion. If A is travelling tangential to B on an intercept vector, then that casts a whole new light on the matter.
So nuh!
Gentile or Jew,
O you who turn the wheel and look to windward,
Consider Phlebas, who was once handsome and tall as you...
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Apr 11th, 2001, 07:29 AM
#36
Thread Starter
transcendental analytic
LOL, guess how much fuel is needed to turn ship A to adapt to B's course!
Use
writing software in C++ is like driving rivets into steel beam with a toothpick.
writing haskell makes your life easier:
reverse (p (6*9)) where p x|x==0=""|True=chr (48+z): p y where (y,z)=divMod x 13
To throw away OOP for low level languages is myopia, to keep OOP is hyperopia. To throw away OOP for a high level language is insight.
-
Apr 11th, 2001, 08:18 PM
#37
New Member
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Apr 11th, 2001, 09:19 PM
#38
Hmmmm,,,,,,,
Originally posted by Fox
After the missile left Parksie It does not matter how fast Parksie is, so I'd say just more than the difference between the Parksie and Cenki and thats 0.2c - I'm sure there's something wrong with that so I vote for "very fast" though
Depends on which end of Parksoe it's leaving
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