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Thread: Engineering Mechanics for 1st year R13 syllabus

  1. #1
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    Post Engineering Mechanics for 1st year R13 syllabus

    GOOD START IS HALF DONE!

    So goes a very well known proverb & because I deeply believe its truth, my first class on any subject deals with the meaning of the Subject Name. This time I am taking the revised R13 subject "Engg Mechanics" for 1st year Engineering Students so thought of writing a short essay on its meaning:

    Engineering: I have already explained in previous post - http://bit.ly/shrekant.

    Mechanics: A branch of Physics which deals with the behaviour of objects at macroscopic level.
    It is also known as Classical Mechanics & involves study of objects under the effect of Force, Torque that may result in Stasis (Equilibrium) or Motion (Velocity, Acceleration etc).

    There are various sub branches of Mechanics.
    1. Mechanics of Rigid Objects
    . . . a. Statics: Study of objects @ rest.
    . . . b. Dynamics: Study of objects in motion.
    . . . . . . (i). Kinematics: Causes of motion are not considered. i.e we study Geometry in motion - Position/Displacement, Velocity, Acceleration etc...
    . . . . . . (ii). Kinetics: Causes of motion are considered. i.e. we study Force/Torque resulting due to inertia & other effects like friction etc.
    2. Mechanics of Solids (Deformable objects) OR Strength of Materials
    Mechanics of Fluids

    Lets come straight to the point. Engineering Mechanics is mostly the study of rigid objects. But in the revised syllabus of R13, JNTU has added some extra topics. So here & there we may have to deal with some deformable objects i.e. belts & springs.

    Rigid objects are like superman i.e. unbendable & similar to the superman they are imaginary. Now if none of the existing materials is perfectly rigid. Then why do we study them? Well, while calculating the forces acting at different parts of an object it makes the problem solving easy if we neglect the deflections. To do that the objects are assumed to be rigid.

    Going by the Revised syllabus there's no single definition of Engineering Mechanics. You may just assume you'll be learning almost all the basics you'll need to understand other subjects like Theory of Machines, Mechanics of Solids, Fluid Mechanics, Design of Machines etc. i.e. whichever subjects deal with forces/torques & their effects.

    Basics needed: To understand Engineering Mechanics you must be profecient in some school fundamentals like Geometry, Trigonometry, Calculus, Units & Conversions etc... I have mentioned unitwise details in a pdf file here - https://drive.google.com/file/d/0Bw1...it?usp=sharing

    There are some very good videos available at http://academicearth.org/courses/phy...cal-mechanics/ . These are video recordings of a class in progress. Classes are taken by an eminent Scientist Walter Levin who even proves the theories with Practical Experiments. Right in Class.

    Another worthy mention is of the https://www.khanacademy.org/science/physics started by Salman Khan. Not the hero of "Bodygaurd" or "Ek thha Tiger" fame but another great personality with his own story. In his own words, he had started making video tutorials just for his cousins and having found good response left his main job to work Full-Time on Tutoring students all over the world. The video below shows him on TED talks - a world famous show which portrays ideas and people who changed the world.

    The revised syllabus of R13 proposed by JNTU consists of 5 units.
    1. Force/Torque & their Resultant/Equillibrium
    2. Friction & Power Transmission
    3. Centroids & Moments of Inertia
    4. Kinematics & Kinetics
    5. Work/Energy & Vibrations

    Download https://drive.google.com/file/d/0Bw1...it?usp=sharing the Session Plan from the given link. It contains the topics & number of classes required to complete them. Along with the basics needed to understand it completely. So that before attending the class for that particular topic you may brush up with the basics from your school or pre-university/intermediate books.

    Hope you'll enjoy the subject. Will keep posting as I go ahead with different units.

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    You can post any questions about the subject you have. I'll try to give an easiest answer.

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    Force
    Lets take a basic approach by trying to reason out what is force & how it can be fully defined.
    Visit my blog for more http://bit.ly/fundamech

    Force: A push or pull applied on an object.

    We can have more force or less force i.e. it can be compared. Hence a force is a quantity. Ex: The force needed to lift a mountain is too much & the force needed to lift a feather is very very small. Apart from these extremes there are numerous little differences that forces can have.

    So how do we compare quantities that differ by small amount?
    Simple – divide one with other & tell the ratio. Say, the force to lift mountain is a thousand or lakh (depending on difference) times that to lift a feather.

    So now you can compare. But what if we have more than 3 values to be compared?
    Hm… this way we’d have more than 3 ratios & keeping track of them’d be difficult.

    So what to do?
    Simple – chose a standard value of quantity & find ratios of all others with respect to that standard. This standard value of a quantity is called a unit. The unit of a force is N (newton) which is the force which results in acceleration of 1 m/s^2 when acting on a mass of 1kg. i.e. 1 N = 1 Kg.m/s^2.

    Every quantity can be given a fixed unit & all the differences can be represented as a ratio, a numerical value multiplied with the unit quantity, which is called Magnitude. Ex: if a force is 20 N, it means that the force is 20 times a newton & 20 N is its magnitude.

    But wait, force is more. Just a magnitude is not enough to define it. We need a direction as well. Ex: applying force in one direction closes the door, but apply it in reverse direction & door will open.

    The result of the two forces is different, so they can’t be same. Even though they have the same magnitude they have two entirely different quantities. Again the opposites are just extremes, forces may have all the small differences in their directions. The directions may sometimes also be in 3 Dimensions.

    The quantities which need a magnitude as well as a direction for getting fully defined are called as vectors. So, force is a vector.

    So we know following points about force:

    - Its a push or pull that may result in acceleration i.e. change of velocity &/or direction.
    - Its unit is N (newton) which is Kg.m/s^2.
    - Its a vector quantity – magnitude & direction both are required.
    - For a force, a 3rd & final requirement is point of application.
    Last edited by cadimator; 11-12-2013 at 12:07 PM.

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    Mass vs Weight! What’s the difference…

    For more visit:
    bit.ly/shrekant = For more such lab & subject material
    bit.ly/cadmate = For youtube video tutorials
    bit.ly/fundamech = For understanding fundamentals

    Seem to have caught the bull by its horns. I was as usual complaining that the students were dull since they didn’t raise a question. Bang came this question:

    Weight vs Mass! What’s the difference?

    Luckily I had the answer ready & since there are always some misconceptions when people use these words, I thought to clear them.

    __________________________________________________ _____________________________

    Weight is actually the force with which earth pulls an object towards it’s center. Also called as Gravitational Force.

    i.e: Weight = Gravitational Force

    Mass on the other hand is the amount of matter.

    If you shift to moon, your mass remains same but weight gets reduced.
    (That’s because all the matter that makes YOU is there on the moon also. But since moon has lesser gravity & hence less acceleration due to gravity, your weight would reduce accordingly. i.e You will feel yourself as lighter.)

    __________________________________________________ ______________________________

    WANT TO WONDER MORE? Read on…

    Many a times you must have measured your weight in Kgs but science mentions Kg as a unit of mass! What’s all the confusion? Read on to find:

    WRONG: Technically it’s wrong when people say their weight is 50 kg.

    RIGHT: The technically correct statement would be that their weight is 50 kgf (Kilogram Force), on earth also mentioning the acceleration due to gravity where the weight is measured (U c, acceleration due to gravity changes from equator to the poles).

    Alternatively, would it be technically right if we say “My mass is 50 kg”?

    WRONG: Well, if you have used a spring balance to measure it then NO. Because the spring balance depends on the effect of gravity & unless its calibrated to suit the acceleration due to gravity of the place, it wouldn’t give exact value of mass.

    RIGHT: If however you measured it by a weight balance putting equal mass of stones on the other side, the effect of change in acceleration would cancel out. i.e. a balance is free of gravity error. You can even do so on moon (if you carry the stones having same mass as your weight & a balance to the moon the balance would agree on the moon also)

    Hope you were able to learn something new. Thanks for reading.
    Last edited by cadimator; 11-16-2013 at 10:01 PM. Reason: missed including an important point

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