Calculate L using Omega, Lo = 16, and h = 1.5

  • Thread starter Thread starter eddievic
  • Start date Start date
Join the discussion
Registration is free. Start your own thread to ask a follow-up.
4 replies · 2K views
eddievic
Messages
47
Reaction score
0
Find L if...

Homework Statement



[tex]\omega=\frac{1}{h}In(\frac{L}{Lo}-1)[/tex]

Find L if omega - -2.6, Lo = 16 and h = 1.5

Homework Equations





The Attempt at a Solution



-2.6*1.5=In(L/16-1)
-3.9=In(L/16-1
e^-3.9=L/16-1
0.02024=L/16-1
1.02024=L/16
so L=16.32384
 
Physics news on Phys.org
The correct abbreviation for the natural log is 'lower case L' and 'lower case N'. You have 'Upper case I' and 'lower case N', which is incorrect. Otherwise, your algebra appears to be correct.
 
SteamKing said:
The correct abbreviation for the natural log is 'lower case L' and 'lower case N'. You have 'Upper case I' and 'lower case N', which is incorrect. Otherwise, your algebra appears to be correct.

Ok thanks for the help I will use the correct abbreviation in future
 
eddievic said:

Homework Statement



[tex]\omega=\frac{1}{h}In(\frac{L}{Lo}-1)[/tex]

Find L if omega - -2.6, Lo = 16 and h = 1.5

Homework Equations


The Attempt at a Solution



-2.6*1.5=In(L/16-1)
-3.9=In(L/16-1
e^-3.9=L/16-1
0.02024=L/16-1
1.02024=L/16
so L=16.32384

It's best to substitute the constants at the end of your algebraic manipulation. Doing so sooner can lead to round-off errors.

This is the way I would have done it.
$$\omega=\frac{1}{h}\ln(\frac{L}{L_0}-1)$$
$$\Rightarrow h \omega = \ln(\frac{L}{L_0}-1)$$
$$\Rightarrow e^{h \omega} = \frac{L}{L_0}-1$$
$$\Rightarrow e^{h \omega} + 1 = \frac{L}{L_0}$$
$$\Rightarrow L_0 (e^{h \omega} + 1) = L$$
Now you can replace the constants.
 
Mark44 said:
It's best to substitute the constants at the end of your algebraic manipulation. Doing so sooner can lead to round-off errors.

This is the way I would have done it.
$$\omega=\frac{1}{h}\ln(\frac{L}{L_0}-1)$$
$$\Rightarrow h \omega = \ln(\frac{L}{L_0}-1)$$
$$\Rightarrow e^{h \omega} = \frac{L}{L_0}-1$$
$$\Rightarrow e^{h \omega} + 1 = \frac{L}{L_0}$$
$$\Rightarrow L_0 (e^{h \omega} + 1) = L$$
Now you can replace the constants.

this makes a lot of sense thanks Mark44