# Stumped on a simple harmonic motion question

• September 21st 2009, 04:35 PM
xxlvh
Stumped on a simple harmonic motion question
$mg = k\Delta\l$
And I obtained 5314 N/m.
After that, I calculated $v_{max}$ by using:
$v_{max} = A\sqrt{\frac{k}{m}}$
• September 21st 2009, 05:05 PM
skeeter
Quote:

Originally Posted by xxlvh
A proud deep-sea fisherman hangs a 65.0 kg fish from an ideal spring having negligible mass. The fish stretches the spring 0.120 m. The fish is now pulled down 5.00 cm and released. What is the maximum velocity it will reach?

No idea where I am going wrong here. First, I solved for the spring constant:
$mg = k\Delta\l$
And I obtained 5314 N/m.
After that, I calculated $v_{max}$ by using:
$v_{max} = A\sqrt{\frac{k}{m}}$
With 0.17 m as the Amplitude and I got 1.54 m/s as the answer, which is incorrect. I also tried using conservation of energy formulas, only to get the same answer. Can anyone help me out??

$k = \frac{mg}{\Delta x} = \frac{65 \cdot 9.8}{.12} = 5308.3$ N/m

the fish is pulled down 5.0 cm = 0.05 m down from equilibrium ...

$A = 0.05$ m

amplitude is measured from equilibrium, not the unstretched position of the spring.

$v_{max} = A\omega = 0.05\sqrt{\frac{5308.3}{65}}$
• September 21st 2009, 05:45 PM
xxlvh
Yiikes I need to pay closer attention. Thank you very much!