(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

With a block of mass m, the frequency of a block-spring system is 1.5Hz. When 80g is added, the frequency drops to 0.9Hz. Find m and the spring constant k.

2. Relevant equations

T=1/f

w=2pi/T

so w= 2pi*f

w^2=k/m

so k=mw^2

T=2pi*sqrt(m/k)

3. The attempt at a solution

The problem seems simple enough. I just have to set up 2 equations to solve one unknown and then find the other right?

So first i found the w for when the mass= m and f= 1.5Hz (i called this w) and the w for when mass= m+0.08 and f= 0.9Hz (W).

Using the formula w= 2pi*f, i found 9.42 for w and 5.65 for W.

Then I set up the 2 equations:

k = mw^2 = 88.8m

and

k = (m+0.08)W^2 = 31.9m + 2.55

After i did equation 1 = equation 2, so:

88.8m = 31.9m + 2.55 and this gave me m=22.3

But the correct answer for m is supposed to be 0.045 kg. Can somebody let me know what I'm doing wrong please?

The correct value for k is supposed to be 3.99N/m

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: SHM mass and spring constant with given frequency

**Physics Forums | Science Articles, Homework Help, Discussion**