chap 3 design of machine elements subjected to bending
TRANSCRIPT
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CHAPTER 3DESIGN OF MACHINE ELEMENTS
SUBJECTED TO BENDING
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
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MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Aim:
To understand how the three types of levers work and appreciate the
advantages/disadvantages of each one.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Expected Knowledge• Force
• VelocityKey Vocabulary
• Lever• Fulcrum
• Resistance• Effort
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Levers are…
• Simple machines that help us apply force.
• Rigid structures, hinged at some part with forces applied at two other points.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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We have levers within our body, and also use them externally for many different
reasons.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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All levers have three parts:
• Fulcrum • Resistance
• Effort
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
![Page 8: Chap 3 design of machine elements subjected to bending](https://reader036.vdocuments.site/reader036/viewer/2022062308/55ce3362bb61ebf14c8b45f3/html5/thumbnails/8.jpg)
Fulcrum
The pivot point.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Resistance (or load)
The weight that needs to be moved.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Effort
The force that is applied to move the resistance (or load).
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Levers perform two main functions:
To increase the resistance
(or force) that can be moved with a given effort e.g. a crowbar.
To increase the velocity at
which an object will move with a
given force. E.g. A golf club.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
FUNCTIONS of Levers
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There are 3 classes of levers.
Each is structured in a different manner and has different
advantages.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
CLASSES of Levers
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The fulcrum lies between the effort and the resistance.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
First class Lever
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First Class Levers
Using a crowbar to move a rock.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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First Class Levers
Using a hammer to pull out a nail.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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First Class Levers
A see-saw.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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First Class Levers
Up and down movement of the head about the atlas joint.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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First Class Levers
Pulling an oar in a row boat.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Second Class Levers
The resistance lies between the fulcrum and the point of effort.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Second Class Levers
The movement of the foot when walking.
(the calf muscle provides the effort and the ball of the foot is the pivot)
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Second Class Levers
Opening a door by the handle.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Second Class Levers
Opening a bottle with a bottle opener.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Second Class Levers
Pushing a wheel barrow.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Third Class Levers
The effort lies between the resistance and the fulcrum.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Third Class Levers
Biceps curl.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Third Class Levers
Fishing with a rod.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Third Class Levers
SUDHIR PATEL L.J.
POLYTECHNIC,A'BAD
Swinging a bat to hit a ball.
Principle of Levers
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Application
Long levers
provide amplified power at the expense of speed of movement of the object being
moved.
Examples: – Using a jack to lift a crashed car.– Using a knife to get the lid off a tin.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
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Application
Short leversprovide speed
at the expense of power
Example: Levers designed to accelerate objects include:- Most body limbs used for throwing or
kicking because the muscle inserts near the pivot point.
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers
![Page 30: Chap 3 design of machine elements subjected to bending](https://reader036.vdocuments.site/reader036/viewer/2022062308/55ce3362bb61ebf14c8b45f3/html5/thumbnails/30.jpg)
Application
• Can you think of sporting examples where there are longer and shorter levers?
• What happens to the effectiveness of a lever if the fulcrum is moved closer or further away from the load?
MISSAM RAZA Dept. -Mechanical LJ Polytechnic
Principle of Levers