Calculating Moments and Resolving Forces in Engineering Statics

In summary, the conversation is about a question involving resolving forces into components and using the equation M = Fd. The person provides their attempt at solving the problem, which involves calculating the moments created by the individual elements of R. They also mention getting stuck and asking for help. The expert gives advice and points out a mistake in the person's calculation, which leads to them getting the correct answer.
  • #1
andrew.c
46
0

Homework Statement




http://img512.imageshack.us/img512/2617/staticsquestion4.jpg [Broken]


Homework Equations


- Ability to resolve forces into components
- M = Fd


The Attempt at a Solution


(a)
Resolve the force acting at an angle into components...
10kN force = -10cos50i - 10 sin 50 j kN

Therefore, resultant R becomes...

= (-10cos50)i + (15 - 3 - 10 sin 50)j kN
= -6.428i + 4.3396j kN

(with a magnitude of 7.756kN)

(b) This is where I get stuck.

I basically calculated the moments created by the individual elements of R,

F1 = 15kn force
F2 = 3kn force
F3 = vertical component 10kn force
and, because I am using the joint with the wall as an origin, the line of action of the horizontal component passes through my origin thus no moment.

M1 = 15*3 = 45kNm
M2 = -3*1.5 = -4.5kNm
M3 = (-10 sin 50)*9 = -68.944kNm

Sum of moments = 45 - 4.5 - 68.944 = -28.444kNm

and then I get stuck. Do you add the moment you've just found to the moment provide in the couple, then sub. back into M=Fd where F=R?

Help!
 
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  • #2
andrew.c: Nice work. The answer to the question in your last paragraph is yes. Also, notice a mistake in your M2 equation.
 
  • #3
nvn said:
Also, notice a mistake in your M2 equation.

Yes, should use 4.5, not 1.5.
Thanks, I got the right answer!
 

1. What is the purpose of studying Engineering Statics?

The purpose of studying Engineering Statics is to understand the behavior of stationary objects and systems under the influence of external forces. This is essential for designing and analyzing structures such as buildings, bridges, and machines.

2. What are the basic principles of Engineering Statics?

The basic principles of Engineering Statics include the concepts of equilibrium, force, moment, and displacement. These principles help in solving problems related to the stability and balance of objects and structures.

3. How is Engineering Statics different from Engineering Dynamics?

Engineering Statics deals with objects and systems that are stationary or in a state of constant motion, while Engineering Dynamics deals with objects and systems in motion or undergoing acceleration. In other words, Engineering Statics focuses on the forces and moments acting on stationary objects, while Engineering Dynamics focuses on the forces that cause motion.

4. What are some common applications of Engineering Statics?

Engineering Statics is used in various fields such as civil engineering, mechanical engineering, aerospace engineering, and structural engineering. Some common applications include calculating the stability of buildings and bridges, determining the load capacity of machines, and analyzing the forces on aircraft structures.

5. How can I improve my understanding of Engineering Statics?

To improve your understanding of Engineering Statics, it is important to practice solving problems and applying the principles learned in class. You can also seek help from your professors or join study groups to discuss and clarify any doubts. Additionally, using visual aids such as diagrams and simulations can also aid in understanding complex concepts.

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