Equilibrium of Forces: Solving for VA and VD in a Statics Problem

  • Thread starter Thread starter chetzread
  • Start date Start date
  • Tags Tags
    Equilibrium Forces
Click For Summary
SUMMARY

The discussion focuses on solving for the vertical reaction forces VA and VD in a statics problem involving equilibrium of forces. The user initially calculated VA as 90.6 N upwards and VD as -185 N downwards, leading to an incorrect total of -94.4 N instead of the expected 147.5 N. Key errors identified include neglecting the contribution of a 10 kN load at 1.3 m from point D and the need to consider the contribution from VA when summing moments about point C. The correct approach involves summing moments about point A for accurate calculations.

PREREQUISITES
  • Understanding of static equilibrium principles in mechanics
  • Familiarity with calculating moments and forces in statics problems
  • Knowledge of reaction forces and their significance in structural analysis
  • Ability to apply Newton's laws to solve for unknown forces
NEXT STEPS
  • Study the method of sections in statics for analyzing forces in structures
  • Learn about calculating moments about different points in a system
  • Explore the concept of distributed loads and their effects on reaction forces
  • Review examples of equilibrium problems involving multiple forces and moments
USEFUL FOR

Students studying engineering mechanics, particularly those focusing on statics and structural analysis, as well as professionals involved in civil and mechanical engineering who require a solid understanding of force equilibrium.

chetzread
Messages
798
Reaction score
1

Homework Statement


I couldn't get the forces in equlibrium in this question

Homework Equations

The Attempt at a Solution


VA + VD = 35(3.5) + 10+15 = 147.5

sum of moment about D = -35(3.5)(1.75+ 3.7) +15(1) + VA(3.5 + 1.7+ 2) = 0
VA = 90.6upwards

Sum of moment about C = -35(3.5)(1.75+1.7) +10(0.7) -VD(2) +15(3) =0
VD = -185 ( downwards) ,

So, VA + VD = -185+ 90.6 = -94.4

So , VA + VD = 90.6 -185 = -94.4N , which is not 147.5N , which part of my working is wrong ?
 

Attachments

  • IMG_20161016_092452.jpg
    IMG_20161016_092452.jpg
    34.1 KB · Views: 439
Last edited by a moderator:
Physics news on Phys.org
Which part of my working is wrong ?
 
chetzread said:

Homework Statement


I couldn't get the forces in equlibrium in this question

Homework Equations

The Attempt at a Solution


VA + VD = 35(3.5) + 10+15 = 147.5
ok
sum of moment about D = -35(3.5)(1.75+ 3.7) +15(1) + VA(3.5 + 1.7+ 2) = 0
VA = 90.6upwards
you forgot the contribution of the 10 kN load at 1.3 m from D
Sum of moment about C = -35(3.5)(1.75+1.7) +10(0.7) -VD(2) +15(3) =0
VD = -185 ( downwards) ,
you forgot he contribution from VA. It's best to sum moments about A.
So, VA + VD = -185+ 90.6 = -94.4

So , VA + VD = 90.6 -185 = -94.4N , which is not 147.5N , which part of my working is wrong ?
see above
 
  • Like
Likes   Reactions: chetzread

Similar threads

  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 3 ·
Replies
3
Views
6K
  • · Replies 1 ·
Replies
1
Views
10K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 41 ·
2
Replies
41
Views
6K
  • · Replies 3 ·
Replies
3
Views
2K