- #1

JoeyBob

- 256

- 29

- Homework Statement
- See attached.

- Relevant Equations
- x(t)=Acos(wt+phi), v(t)=-wAsin(wt+phi)

So first I found the total energy of the system by calculating the potential Energy, Ep=0.5k(l^2+l^2) and get 2.0475 (this part is right).

Then I find w using the period T=2pi/w, so w=2pi/1.21=5.1927

I also found the amplitude using E=1/2kA^2, so A=sqrt(2E/k)=0.212132

Now this is the part I think I am messing up. I go

0.15=Acos(phi) to find phi

Then x(t)=Acos(wt+phi) to find location. But this gives me the wrong answer of -0.14 when the answer should be 0.010.

Another thing that doesn't make sense to me is that I solved the amplitude using E=1/2kA^2, but when I try and solve the amplitude using 0.15=Acos(phi) and 0=-wAsin(phi) I get an amplitude of 0.15, which is different.

Then I find w using the period T=2pi/w, so w=2pi/1.21=5.1927

I also found the amplitude using E=1/2kA^2, so A=sqrt(2E/k)=0.212132

Now this is the part I think I am messing up. I go

0.15=Acos(phi) to find phi

Then x(t)=Acos(wt+phi) to find location. But this gives me the wrong answer of -0.14 when the answer should be 0.010.

Another thing that doesn't make sense to me is that I solved the amplitude using E=1/2kA^2, but when I try and solve the amplitude using 0.15=Acos(phi) and 0=-wAsin(phi) I get an amplitude of 0.15, which is different.