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How to force Wolfram Alpha to read v as a variable

Posted 9 years ago

Hi! So I have a fairly long integral I want to evaluate:

((integral (GMmx/(x^2+r^2)^(3/2) dx)) = 0.5m*v^2) | G = 6.67e-11, M = 2.3e22, m = 59, x = 5.5e8, r = 4.8e8

The problem is, Wolfram Alpha seems to think m represents "metres", and v represents "volts". There's no option to use them as a variable instead. How do I force Wolfram Alpha to use those pronumerals as variables, and not units?

POSTED BY: Eleanor McMurtry
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Thanks for the tips, that helps a lot! My integrand was missing a negative sign, so my final answer is real :)

POSTED BY: Eleanor McMurtry
Posted 9 years ago

When WolframAlpha is confused by the complexity of my query I have sometimes had success solving part of the problem first and then giving it the rest of the problem as a second query.

First I try to find the integral with the appropriate constants, but not defining x to be a constant. I think WA has understood that the symbols are numeric constants and not units.

Find the integral

Then I use the result of that to try to complete the problem

Find the value of v

I worry that I have misinterpreted your problem because of the complex number as a result.

Perhaps you can see how to adapt this technique to solve your problem correctly.

POSTED BY: Bill Simpson
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