Solve Exponentials Problem: ln((V+v)/(V-v)) = 2ctV

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In summary, the conversation is discussing the steps to solve the equation ln((V+v)/(V-v)) = 2ctV and arrive at the solution v = V((e^Vct - e^-Vct)/(e^Vct+e^-Vct)). The hint given is to use the laws of logs and the basic definition of logs to solve the equation.
  • #1
Nevermore
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I have ln((V+v)/(V-v)) = 2ctV, and I've checked this is right. But how do I go from here to v = V((e^Vct - e^-Vct)/(e^Vct+e^-Vct))? The solutions just give them as successive lines.

(I appreciate that's not the easiest thing to read, it's taken from the 2004 MEI specimen paper for A-level Mechanics 4, if that helps.)
 
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  • #2
HINT: Laws of logs;

[tex]\ln\frac{a}{b} = \ln|a| - \ln|b|[/tex]
 
  • #3
OK, so
ln((V+v)/(V-v)) = 2ctV
=> ln(V+v)-ln(V-v) = 2ctV
ln(V)ln(v) - ln(V)/ln(v)
2ln(v) = 2ctV
v = e^Vct

Is this right? Where can I go from here?
 
  • #4
Nevermore said:
OK, so
ln((V+v)/(V-v)) = 2ctV
=> ln(V+v)-ln(V-v) = 2ctV
ln(V)ln(v) - ln(V)/ln(v)
2ln(v) = 2ctV
v = e^Vct

Is this right? Where can I go from here?

there is something wrong in what u have written... first of all
log(a*b) = log(a) + log(b)...what u have used is log(a+b) = log(a) * log(b)..even after that u have written something wrong...check it once more...
anyway u don't need to use that...use the basic definition of logs...
if ln(a) = b
=> e^b = a
 
  • #5
In other words,
[tex]\frac{V+v}{V-v}= e^{2ctV}[/tex]
Solve that for v.
 

FAQ: Solve Exponentials Problem: ln((V+v)/(V-v)) = 2ctV

What does "ln" stand for in this equation?

"ln" stands for natural logarithm, which is the inverse function of the exponential function. It is denoted as "ln(x)" or "loge(x)", where "e" is a mathematical constant approximately equal to 2.71828.

How do I solve for "V" in this equation?

To solve for "V", you need to use the properties of logarithms to isolate "V" on one side of the equation. First, you can use the quotient property of logarithms to rewrite the expression as ln(V+v) - ln(V-v) = 2ctV. Then, you can use the power property to move the exponent outside of the logarithm, giving you ln(V+v) - ln(V-v) = ln(V2ct). Finally, you can use the difference property to simplify the left side of the equation to ln((V+v)/(V-v)) = ln(V2ct). Since logarithms are one-to-one functions, you can equate the arguments of the logarithms to solve for "V".

Can this equation be solved without using logarithms?

Yes, it is possible to solve this equation without using logarithms. You can use the properties of exponents to rewrite the equation as (V+v)/(V-v) = e2ctV. Then, you can cross-multiply and expand the exponential term to get a quadratic equation in terms of "V". However, using logarithms may make the solution process easier and more efficient.

What are the units of measurement for the variables in this equation?

The units of measurement for the variables in this equation depend on the context of the problem. However, typically "V" and "v" represent velocities in units of distance per time (e.g. meters per second), "c" represents the speed of light in a vacuum (approximately 3 x 108 meters per second), and "t" represents time in seconds.

Can this equation be used to solve real-world problems?

Yes, this equation can be used to solve real-world problems involving exponential growth or decay. For example, it could be used to model the population growth of a species or the radioactive decay of a substance. However, it is important to note that the values of the variables in the equation must be consistent with the context of the problem in order for the solution to be meaningful.

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