• Support PF! Buy your school textbooks, materials and every day products Here!

Hydrostatics Problem (Why is this Wrong?)

  • #1
3,003
2
Picture1-32.png


In calculating the vertical force component, you want to find the weight of the missing water.

This should be simple: Find the Volume of the missing water and multiply by specific weight.

Why is my volume calculation incorrect? I am using the volume of the rectangular prism whose top coincides with the surface and whose base coincides with B. Then I subtract the volume of the quarter cylinder:

[tex]V_{Tot}=V_{rect}-.25V_{cyl}[/tex]

[tex]V_{rect}=(1.5+0.75)(0.75)(1.2)[/tex]

[tex].25*V_{cyl}=.25*(\pi (0.75)^2(1.2)[/tex]

But this does not give the correct volume. The solution says to use:

Picture2-19.png

I am failing miserably to see how my method is different from theirs? Am I messing up a dimension here?
 

Answers and Replies

  • #2
3,003
2
Aaahhhhhhhh!!!!! My brain!!!!!!

Edit: How does what they wrote even make any sense?

The first term has dimensions of m^3 and the second has dimensions of m^2 !

Not to mention, if you put those numbers into your calculator they do not equal what they are saying they equal. WTF
 
Last edited:
  • #3
Doc Al
Mentor
44,882
1,129
It looks like the second term in their solution has a typo: They left off the factor of 1.2m.
 
  • #4
3,003
2
It looks like the second term in their solution has a typo: They left off the factor of 1.2m.
Yeah. I think that makes it equivalent to mine if you tack that on.

Sometimes it does not help to be able to check your answers. :grumpy:
 

Related Threads for: Hydrostatics Problem (Why is this Wrong?)

  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
7
Views
8K
Replies
17
Views
967
  • Last Post
Replies
1
Views
960
  • Last Post
Replies
5
Views
994
Top