Can anyone help me with these physics problems????

[acejj26]

I need help on these two homework problems I am doing. Seeing as how our professor doesn't teach us anything like this and our book says nothing on damped harmonic motion, I am screwed unless someone can help me.

These are two simple harmonic motion problems. I would appreciate any and all help you guys could give me.

Problem 1

Problem 2

Thanks guys for all help.

 

[Napalm381]

First of all, make it so your links work.
EDIT: Now they work, I just can't read them.

 

[yakko]

Problem 1 = No clue.
Problem 2 = No fscking clue.

 

[acejj26]

Napalm, why can't you read them??

 

[Napalm381]

I can BARELY read them because it is dark type on a dark background in a small picture.

 

[acejj26]

Okay, Napalm. I'll fix it and update. It will take me a minute or two.

 

[acejj26]

Okay, images should be easier to read.

 

[Napalm381]

What the hell is a dashpot? Never seen that before.

 

[DAM]

any way to make them bigger???




dam()

 

[yakko]

Much easier to read now.

Problem 1 = Still no clue.
Problem 2 = Still no fscking clue.

 

[Napalm381]

Well, on problem 2, from the Free Body Diagram (they help! use them!), you have 4 forces:
1. Gravity: F=mg
2. Lower spring: F=-k(x-X1)= -k(x-C cos(wt)), using the given eqn for X1.
3. Upper spring: F=-kx
4. Dashpot: F=-bv = -b*(dx/dt)

Then using Newtons Second Law we can set sum(F)=ma.

m(d2x/dt2)=mg - k(x-C cos(wt)) - kx -b(dx/dt).

How's that for a start?

Are we having fun yet, kids?

 

[acejj26]

I can make them bigger. A dashpot is there to provide the damping force F= -bv. Besides that, it plays no role. The pics will be updated shortly. Thanks guys for giving this an effort.

 

[Napalm381]

<< Besides that, it plays no role >>

I figured it out...and it most certainly plays a role...it's what makes this a damped system.

 

[acejj26]

The pics are uploading right now. Again, I appreciate all your guys' help. I will be working these as well to see if I get answers any of you get. Thanks again.

Josh

 

[acejj26]

Okay, the pics are up and are bigger and easier to read. And about the dashpot, I meant that besides the damping force it provides, it plays no other role (gravitational and normal forces acting on the dashpot can be ignored).

 

[acejj26]

For problem 2, I think that there are two scenarios (am I wrong?):

One with the wheel moving so that the bottom (and the top) springs are stretching;
One with the wheel moving so that the bottom (and the top) springs are contracting.

For the first scenario, I get bv and kx acting up on the mass m and k(x-X1) and mg acting down on the mass m.

For the second scenario, I get k(x-X1) acting up on the mass and mg and kx acting down on the mass m. For this scenario, does bv act up or down???

Any ideas guys??

 

[CirekL]

Two things I learned in Physics Mechanics:
1) F=MA
2) Don't sleep in the front row...
Maybe one of them can answer your problems.

 

[acejj26]

bump

 

[acejj26]

another bump....i need help!!!

 

[Demon-Xanth]

42

 

[acejj26]

Please, no ignorant comments. If you have figured out something to help me, I'd appreciate it. I will be posting some of my work online soon, so someone can critique it or use it to figure out other parts of the problem. Thanks to all.

 

[acejj26]

Here is some of my work...tear it to shreds or use it to help me out. I appreciate everyone's input on this.

Problem 1

Problem 2

Let me know what you guys think.

 

[acejj26]

up

 

[acejj26]

Can anyone check the validity of this work??

Work

 

[Sunny129]

well the first problem is obviously a differential equation. to solve for the inhomogenious solution you must set the driving force = to zero. once yoou have your inhomogenious solutions, replace the driving force given in the original problem and solve. the final solution for x will be the sum of the inhomogenious and homogenious solutions...i dont know if that helps any. those are just the basics to solving a differential dealing with a driving force and simple harmonic motion. now if you can only turn these words into numbers and find a nice solution...lord knows i can't...i hope this helped some...

EDIT, i don't know how to do part B (continuing the graph), and also, i'm taking a look at your work right now...no promises that i can tell if its right or not, but i'll try

2nd edit, i also mixed up the words homogenious and inhomogenious. the homogenious has no driving force, while the inhomogenious does.