Go Back   Physics Help Forum > High School and Pre-University Physics Help > Thermodynamics and Fluid Mechanics

Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

Like Tree1Likes
  • 1 Post By oz93666
Reply
 
LinkBack Thread Tools Display Modes
Old Jan 2nd 2019, 12:42 PM   #1
Junior Member
 
Join Date: Jan 2018
Posts: 5
Question resisting force at a clasp

Hello,

I have the below problem followed by the answer I believe it to be. Would somebody be able to confirm I have got it right as I am not sure??


Hinged water storage is shown below. Its top side is denoted as C, the narrow side as B and the long side as A. Assume water density is 1000 kg/m3 and gravity is 9.81 m/s2 Side A is hinged at the bottom edge and secured using a clasp at its top edge. Dimensions are: L = 1m, H = 0.5m & W = 0.5m



When the tank is full of water:

a) Calculate the required resisting force at the clasp to keep the panel shut.



ANSWER:

Here force along depth of A is varying continuously, so there are 3 forces on tank side.

H=0.5

L=1

W= 0.5

A=0.5m2

y =0.25


1st moment of area =

Area * y = 0.5 *0.25 = 0.125


2nd moment of area =

Iss = Iyy +A(y) 2 = BD3 /12 + BD (y)2

=1* (0.5)3 /12 + 1*0.5 *(0.25)2

=0.04


Center of pressure:

= 2nd moment / 1st moment = 0.04 / 0.125 = 0.328


Total Thrust force

= ρ*g*A* y

= 1000*9.8*0.5*0.25 = 1225 N

The resisting force on the clasp F2.

Resistive Force x Distance from Hinge = Clasp Force x Distance from Hinge

F1 D1 = F2 D2

1225* 0.3 = F2 *0.5

F2 =1225* 0.3 / 0.5

=735 N


( F3 is the Hinge Force = F2 - F1 =1225 -735 = 490 N )
davefrick1 is offline   Reply With Quote
Old Jan 2nd 2019, 07:30 PM   #2
Senior Member
 
Join Date: Apr 2017
Posts: 498
The tank side is 0.5 x 1 .......total area 0.5

Height of tank 0.5m .... pressure at bottom is 9.81 x 0.5 x 1000 = 4905 N/m2

Pressure at top is zero ...average pressure on side is 2452.5 N/m2

total force on side is 0.5 x 2452.5= 1226.25N

We can regard this as pushing at the center of the face...

This force acts about the hinge at the bottom , so the clasp at the top will feel half this force ..... 613.125N

Hmmm ... not sure that's correct!!

The total force on the side is correct , but where will it act??? ...closer to the bottom .... 1/3 rd up !!!

So the force acting 1/3 from bottom is 1226.25 .... force on clasp is therefore 1/3rd of that = 408.75N I think that's right !
topsquark likes this.

Last edited by oz93666; Jan 2nd 2019 at 07:49 PM.
oz93666 is offline   Reply With Quote
Old Apr 25th 2019, 01:51 PM   #3
Junior Member
 
Join Date: Apr 2019
Posts: 1
hi,

Did you get this right in the end? I have the same question.

I have done the same for part A

But part b the forces on hinge and clasp. I cannot find the right answer.
pmc88 is offline   Reply With Quote
Reply

  Physics Help Forum > High School and Pre-University Physics Help > Thermodynamics and Fluid Mechanics

Tags
clasp, force, resisting



Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Normal force and gravity force are not action reaction pairs? jlyu002 Kinematics and Dynamics 6 May 21st 2017 09:21 PM
Is centripetal force opposite but equal in magnitude of centrifugal force? jlyu002 Kinematics and Dynamics 2 Jul 24th 2014 05:17 PM
Im trying to apply a force at the middle a column, how do i predict the maximum force yichenli Equilibrium and Elasticity 4 Sep 13th 2013 03:13 PM
The Slope of a Normal Force vs Applied Force Graph reventon703 Kinematics and Dynamics 1 Apr 11th 2012 05:47 AM
frictional force depending on vertical force maiamorbific Kinematics and Dynamics 1 Oct 3rd 2009 11:32 PM


Facebook Twitter Google+ RSS Feed