# How Do I Solve These Mechanical Principles Problems in Electronic Engineering?

• dj-motion
In summary, the student attempted to calculate the resultant of a load on a beam and found that the resultant was 14KN. For strain, the student got 50.52x10^-6. For shear stress, the student got 381.97MPa.
dj-motion
hey, so I'm currently studying electronic engineering on year 2 of level 3 and having to study mechanical principles this year which I don't really know anything about and my tutor doesn't explain properly. I would appreciate some help on the method of calculating the questions. I've added clear images of the questions as there would be too much to type out

known equations that I need:

R=√(ΣFx^2+ΣFy^2)
θ=tan^-1(ΣFy/ΣFx)

σ=F/A
ε=σ/E
A=πr^2
τ=Fp/Ap
S=τ/Y
Combined Factor of Safety=Sy/(Sx^2 + 3τxy^2)^1/2

Attempt so far, not sure if it's correct but I've tried with limited knowledge about mech p.

a) Σfx=20cos(30) + 10cos(150) -25
=17.32-8.66-25
=-16.34N

Σfy=20sin(30) - 10sin(150) - (f=mg=2(10)=20N)
=10-5-20
= -25

R=√(16.34^2+25^2)
=√(267+625)
=√892
=29.87N

θ=tan^-1(-25/-16.34)
=56.83°

∴R=29.87N at an angle of 56.83° from the positive horizontal axis

b) Equilibrant=29.87N 180+56.83=236.83°

∴E=29.87N at an angle of 236.83° from the positive horizontal axis

C) I didn't really understand the question, I assumed it meant show the resultant on the space diagram but it says calculate so I'm not sure

Taking moments of Rb:

Rb x 12 - 10 x 3 - 5 x (3+3) - (2x6)(9)
∴ 12Rb-30-30-108=0
∴Rb=(30+30+108)/12
=168/12
=14KN

Total load on beam = 10+5+(2x6) = 27KN

Ra+14=27
Ra=27-14
Ra=13KN

a) A=πr^2=π30^2=900π=2827.43mm^2
σ=F/A=(30x10^3)N/(2.827x10^-3)m^2=10.61MPa

b) for strain I got 50.52x10^-6 using ε=σ/E

c) I got 0.126mm using dl=σlo/E

d) for shear stress I got 381.97MPa using τ=Fp/Ap

for shear strain I got 2.73 x 10^-3 using S=τ/y

Couldn't do Task 4 at all, I know there's a lot to read but would appreciate some help on abit of it lol cheers

a) Σfx=20cos(30) + 10cos(150) -25

Look at the diagram again and check the term 10cos(150).

Σfy=20sin(30) - 10sin(150) - (f=mg=2(10)=20N)

ditto the term 10sin(150).

PS Might be better to create separate threads for Task 2, 3, 4.

task 2 looks good; Task 3, you do not have the correct shear force, the pin is in double shear, you are off by a multiple.

thanks guys :) appreciate the help

## 1. What is statics and why is it important for mechanical principles?

Statics is a branch of mechanics that deals with the study of objects at rest or in equilibrium. It is important for mechanical principles because it helps us understand how forces act on structures and objects, and how these forces can be balanced to maintain stability.

## 2. What are the key concepts in statics?

The key concepts in statics include forces, moments, equilibrium, and free body diagrams. Forces are vectors that represent the push or pull on an object. Moments are the rotational effects of forces. Equilibrium is the state in which all forces acting on an object are balanced, resulting in no net force or acceleration. Free body diagrams are graphical representations of an object with all the forces acting on it.

## 3. How does statics relate to real-life applications?

Statics has numerous real-life applications, such as designing and analyzing structures like bridges, buildings, and machines. It is also used in the study of forces acting on the human body and in understanding the stability of objects and structures in everyday life.

## 4. What are the common methods used in solving statics problems?

The common methods used in solving statics problems include the method of joints, method of sections, and the three equations of equilibrium (sum of forces in x, y, and z directions). These methods involve breaking down complex systems into smaller, more manageable parts and applying the principles of equilibrium to solve for unknown forces.

## 5. How can I improve my understanding of statics?

To improve your understanding of statics, it is important to practice solving problems and to have a strong foundation in mathematics and physics. It is also helpful to visualize problems and concepts using free body diagrams and to seek out additional resources, such as textbooks, online tutorials, or study groups.

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