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C6L1V@shaw.ca
science forum Guru

Joined: 23 May 2005
Posts: 628 Posted: Sun Jul 09, 2006 8:11 pm    Post subject: Re: question with velocity. mina_world wrote:
 Quote: hello sir~ maybe, my question look like physics. if a velocity is t (km/h), then the acceleration is 1(km/h^2) by differentiation.

Be careful. This is a problem about changing units. So you are saying
that a time of 1 hour, the object is moving at 1 km/h = 1000 m/3600
sec = 1000/3600 m/sec. In other words, in 3600 sec the speed reaches
1000/3600 m/sec. Therefore, in x seconds, the speed is
(x/3600)(1000/3600) m/sec, so v = (1000/3600^2) x m/sec, where x is
time in seconds. Thus, the acceleration is a = 1000/3600^2 m/sec^2.

R.G. Vickson

 Quote: since t (km/h) = (1000*t)/3600 (m/s), so, the acceleration is 1000/3600 (m/s^2) by differentiation. but i know the fact that 1 (km/h^2) = 1000/(3600^2) (m/s^2). um...i can't my errors. so, i need your advice. mina_world
science forum Guru Wannabe

Joined: 20 Jul 2005
Posts: 186 Posted: Sun Jul 09, 2006 4:03 pm    Post subject: Re: question with velocity. "José Carlos Santos" <jcsantos@fc.up.pt> wrote in message
news:4hcmg7F1qmtngU1@individual.net...
 Quote: mina_world wrote: maybe, my question look like physics. It does, but it is a mathematical question. if a velocity is t (km/h), then the acceleration is 1(km/h^2) by differentiation. since t (km/h) = (1000*t)/3600 (m/s), This is where the problem lies. The letter _t_ on the left is the time measured in hours. The letter _t_ on the right *should be* the time measured in *seconds*, rather than in hours. So, you should have: t (km/h) = (1000*(t/3600))/3600 (m/s) Now it is correct. After, say 2 hours, what's the speed? The left side says it is 2 km/h and the right side says it is 2*1000/3600 m/s, which is correct (that is, they're equal). so, the acceleration is 1000/3600 (m/s^2) by differentiation. but i know the fact that 1 (km/h^2) = 1000/(3600^2) (m/s^2).

yes, i see. thank you very much. José Carlos Santos
science forum Guru

Joined: 25 Mar 2005
Posts: 1111 Posted: Sun Jul 09, 2006 3:43 pm    Post subject: Re: question with velocity. mina_world wrote:

 Quote: maybe, my question look like physics.

It does, but it is a mathematical question.

 Quote: if a velocity is t (km/h), then the acceleration is 1(km/h^2) by differentiation. since t (km/h) = (1000*t)/3600 (m/s),

This is where the problem lies. The letter _t_ on the left is the time
measured in hours. The letter _t_ on the right *should be* the time
measured in *seconds*, rather than in hours. So, you should have:

t (km/h) = (1000*(t/3600))/3600 (m/s)

Now it is correct. After, say 2 hours, what's the speed? The left side
says it is 2 km/h and the right side says it is 2*1000/3600 m/s, which
is correct (that is, they're equal).

 Quote: so, the acceleration is 1000/3600 (m/s^2) by differentiation. but i know the fact that 1 (km/h^2) = 1000/(3600^2) (m/s^2).

Best regards,

Jose Carlos Santos mina_world
science forum Guru Wannabe

Joined: 20 Jul 2005
Posts: 186 Posted: Sun Jul 09, 2006 3:27 pm    Post subject: question with velocity. hello sir~ maybe, my question look like physics. if a velocity is t (km/h), then the acceleration is 1(km/h^2) by differentiation. since t (km/h) = (1000*t)/3600 (m/s), so, the acceleration is 1000/3600 (m/s^2) by differentiation. but i know the fact that 1 (km/h^2) = 1000/(3600^2) (m/s^2). um...i can't my errors. so, i need your advice.  Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First
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