BF2S Forums Need help with my physics homework

-Sh1fty- wrote:

Hey folks!

Right so I have a physics test on Monday and Google seems to hate me. So the subject is speed. Basically there's tons of theories and diagrams and shit. But the one thing I can't do is:

Two trains are heading at each other, there's 80km separating them. Train A is heading 54km/h and train B is heading 72km/h. They're traveling at this constant speed over the 80kms.

Could somebody please explain how to work this problem please? I know one way to do it by making a diagram with an x and y axis and slowly doing it that way but I need the formula.

I'll continue to search Google now.

Thanks guys.

What is the actual problem? You've just given us the conditions...

Flaming_Maniac wrote:

final speed is 0 for both with 72 casualties

Well they will cross in about 9000 seconds, but to be honest I don't see it happening

They're on separate tracks running parallel

CanadianLoser wrote:

it takes 38.5 minutes for them to hit

Ok great but I need to know HOW you arrived at that. What formulas or stuff did you use?

Are you at least drawing diagrams?

Ahhh my brain's going to blow

lol @ boom

Ahhh damn I think I need a break from this stupid exercise it's doing my head in :'(

Thanks for the awsm picture BTW. I'll try and use the same method with the bicycles.

=NHB=Shadow wrote:

"pi"

wat

DrunkFace wrote:

=NHB=Shadow wrote:

"pi"

wat

¯\(°_o)/¯ I dunno, lol

KuSTaV wrote:

mcminty wrote:

Are you at least drawing diagrams?

http://i47.tinypic.com/zu5y5u.jpg

s is what real men use.

lol, I know.. but for the sake of not confusing him I used a common algebraic variable in my diagram.


_{but yea, I should have initially said s = vt..}

liquidat0r wrote:

DrunkFace wrote:

=NHB=Shadow wrote:

"pi"

wat

I think he must have meant x, lol

x's are written like that so they are not confused with the cross product

I don't think I learned the cross or dot product in HS...

and they certainly wouldn't teach vector multiplication BEFORE simple things like velocity and displacement


ed: While Minty's drawing and calculations are good.. they're unnecessary

Do what canadianloser said. 72t + 54t = 80km. At the point where the trains meet, the two of them combined cover the entire 80km, and t is equal.
80km/126 = t. t = .6349, or multiply by 60 for minutes. (38.1 minutes)

double edit: from there you can simply multiply speed by the t to find the distance each of them covered, which if you check your answer should come out to 80km.

Last edited by Bevo (2010-02-25 07:48:59)

Ok but what about the bicycle problem? I'm still sort of lost. Minty helped but I'm still confused.

A cyclist leaves the town of Ouchy towards Cully at 15:00. His average speed is 18km/h. Another man is walking from Cully to Ouchy and he leaves at 14:30. His average speed is 7.2km/h.

The distance separating the two towns is 10km.

I'm so freaking bad at this. T = time right? So what the hell does 72t mean? 72 * t?

No way I'm ever passing this fucking school, why did I ever take these extra courses? I just wanted to finish a year earlier...