## ajprincess 3 years ago 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

1. ajprincess

Here |dw:1352046269529:dw|

2. hartnn

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

3. ajprincess

oops sorry forgot to post the question

4. ajprincess

Determine the operating speed of the fan.

5. ajprincess

|dw:1352046585292:dw| Am I right?

6. hartnn

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

7. ajprincess

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

8. hartnn

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

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

10. hartnn

right ?

11. ajprincess

ya

12. ajprincess

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

13. hartnn

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

so what equation should be used here @hartnn?

15. hartnn

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

Ha k. Thanxxxxx a lot for helping me:)

17. hartnn

welcome ^_^