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

  • Thread starter Thread starter lc99
  • Start date Start date
AI Thread Summary
The discussion revolves around a student's concerns about converting units incorrectly on a statics exam question. The student converted lengths from millimeters to meters but did not adjust the torque value from 450 N-m to 0.450 kN-m, leading to discrepancies in their final answers. Other participants confirm that while converting mm to m is acceptable, failing to convert the torque value affects the results significantly. The student realizes that this oversight caused their calculated support forces to be incorrect. Overall, the conversation emphasizes the importance of consistent unit conversion in statics problems.
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: 742
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
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Back
Top