Did i do this question completely wrong? (Statics-moment)

  • Thread starter Thread starter lc99
  • Start date Start date
Click For Summary
SUMMARY

The discussion centers on a student's confusion regarding unit conversion in a statics problem from their final exam. The student initially used millimeters for lengths while keeping forces in kilonewtons and moments in newton-meters, leading to incorrect calculations. A key takeaway is that when using kilonewtons for forces, the moment should also be converted to kilonewton-meters for consistency. The student realized that failing to convert the moment from 450 N-m to 0.450 kN-m contributed to their incorrect results.

PREREQUISITES
  • Understanding of statics principles, particularly force and moment calculations
  • Familiarity with unit conversions, specifically between millimeters and meters
  • Knowledge of using kilonewtons (kN) and newton-meters (N-m) in engineering problems
  • Ability to analyze shear and bending moment diagrams
NEXT STEPS
  • Review unit conversion techniques in engineering mechanics
  • Study the relationship between forces and moments in statics
  • Learn how to correctly apply the principles of shear and bending moment analysis
  • Practice solving statics problems with mixed units to avoid common pitfalls
USEFUL FOR

This discussion is beneficial for engineering students, particularly those studying statics, as well as educators who teach unit conversion and problem-solving techniques in mechanics.

lc99
Messages
161
Reaction score
3

Homework Statement


upload_2018-5-7_20-32-5.png


Homework Equations

The Attempt at a Solution



I had this question on my final exam and i think i got the wrong numbers because i converted the mm into meters for all of them. So i kept F=3kN , 450N*m , and 3kN as is and used meters instead of mm for the lengths. Would this affect my final answer?
 

Attachments

  • upload_2018-5-7_20-32-5.png
    upload_2018-5-7_20-32-5.png
    10.6 KB · Views: 772
Physics news on Phys.org
lc99 said:

Homework Statement


View attachment 225356

Homework Equations

The Attempt at a Solution



I had this question on my final exam and i think i got the wrong numbers because i converted the mm into meters for all of them. So i kept F=3kN , 450N*m , and 3kN as is and used meters instead of mm for the lengths. Would this affect my final answer?
What was your final answer?
If that was your only mistake, you should get some worthwhile credit.
 
Changing mm to m is fine but if you use force in kN, then your 450 N-m couple should be converted to 0.450 kN-m. Did you do that?
 
haruspex said:
What was your final answer?
If that was your only mistake, you should get some worthwhile credit.
For normal force A , i got like -474 kN . So basically i got the wrong support forces and so i used the wrong numbers.
 
PhanthomJay said:
Changing mm to m is fine but if you use force in kN, then your 450 N-m couple should be converted to 0.450 kN-m. Did you do that?
Ahh man. I did not do that. Uhgh. No wonder nothing matched up.

I did all the steps that needed to be done like finding the equations for shear and bending moments. But it just did not match up with the actual problem. UGH
 

Similar threads

Fluids: Concept about Fluid Pressure in a relation with Force and Area
  • · Replies 6 ·
Replies
6
Views
3K
Question About Beginner Static Problems
  • · Replies 2 ·
Replies
2
Views
1K
Image with an Plano-Convex lens
  • · Replies 7 ·
Replies
7
Views
3K
How do I find the intersection of the wrench's LOA?
  • · Replies 4 ·
Replies
4
Views
1K
Components of the equivalent moment at a point
  • · Replies 3 ·
Replies
3
Views
2K
Why does the coefficient for steel in expansion change with temperature?
  • · Replies 2 ·
Replies
2
Views
1K
Determine the mass moment of inertia of the assembly
  • · Replies 6 ·
Replies
6
Views
8K
Calculating Dimensions of Titanium Disk Under Load
  • · Replies 6 ·
Replies
6
Views
2K
Change in Entropy When Mixing Water at Different Temperatures
  • · Replies 5 ·
Replies
5
Views
1K
Distance of the final image in a compound microscope
  • · Replies 3 ·
Replies
3
Views
5K