## ajprincess Group Title Please help:). the maximum amplitude and the maximum acceleration of the foundation of an industrial fan were found to be x_max=0.2mm and a_max=0.3 one year ago one year ago

1. ajprincess Group Title

Here |dw:1352046269529:dw|

2. hartnn Group Title

so whats the question, that is correct $$a=\ddot x$$ where differentiation is w.r.t time.

3. ajprincess Group Title

oops sorry forgot to post the question

4. ajprincess Group Title

Determine the operating speed of the fan.

5. ajprincess Group Title

|dw:1352046585292:dw| Am I right?

6. hartnn Group Title

if u take x as sinusoidal, then x_max = A=0.2mm are you suppose to take it as sinusoidal ?

7. ajprincess Group Title

i am nt sure. Bt in the answr given they use $$x=Acos(\omega t)$$ i dnt get why they use it.

8. hartnn Group Title

i would write that in this manner , you are correct numerically. |x|=A , $$|\ddot x |=Aw^2$$ so w^2= 0.3/0.2 as A=0.2 and $$|\ddot x |=0.3$$

9. hartnn Group Title

and this speed you will get it in rad/sec ofcourse by taking sqrt of w^2

10. hartnn Group Title

right ?

11. ajprincess Group Title

ya

12. ajprincess Group Title

where do we use $$x=Asin\omega t$$ and $$x=Acos\omega t$$? Are they equal? I am nt getting this.

13. hartnn Group Title

they aren't equal. just phase shift of pi/2 so either of them can be used. but in this question even it doesn't make sense to me using sinusoidal wave for fan equation, if it is given, then its ok.

14. ajprincess Group Title

so what equation should be used here @hartnn?

15. hartnn Group Title

not sure, need to google it ..but since in your given answer sine waves are used, your teacher/course must expect u to take it as sinusoidal everytime....

16. ajprincess Group Title

Ha k. Thanxxxxx a lot for helping me:)

17. hartnn Group Title

welcome ^_^