Help with a formula

  • Thread starter blue88
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  • #1
blue88
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I need to derive this formula:

x = (sqrt of 2h/g)v

from these two equations:

h = .5gt^2

x = vt


Thanks... just can't figure this out!
 

Answers and Replies

  • #2
stunner5000pt
1,455
2
do you mean [tex] \sqrt{\frac{2h}{g}} v [/tex]

Start off with the first equation. Replace what can be replaced in this equation. Rearrange and you're there!
 
Last edited:
  • #3
blue88
8
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yes, this is the formula, it was for a lab so we were using x as a distance
 
  • #4
TD
Homework Helper
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Rewrite the first equation for t, I took the positive root:

[tex]h = \frac{{gt^2 }}
{2} \Leftrightarrow t^2 = \frac{{2h}}
{g} \Leftrightarrow t = \sqrt {\frac{{2h}}
{g}} [/tex]

All that's left is substituting it in [itex]x = vt[/itex]
 
  • #5
blue88
8
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but there is no way to combine the x=vt with it?
 
  • #6
TD
Homework Helper
1,022
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That's what you have to do now. Substitute the expression we found for t in the formula x = vt...
 
  • #7
quantumdude
Staff Emeritus
Science Advisor
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Yes, there is. Take [itex]x=vt[/itex] and solve for [itex]t[/itex], then substitute.
 
  • #8
Poncho
29
0
Are you kiddin' me, buddy? How about [tex]t = \frac{{x}}
{v} [/tex]
 
  • #9
blue88
8
0
but i need to derive this formula:

x = (sqrt of 2h/g)v

from these two equations:

h = .5gt^2

x = vt


i still don't understand how to do that
 
  • #10
quantumdude
Staff Emeritus
Science Advisor
Gold Member
5,575
23
The complete solution is right here in this thread.
 

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