Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Diploma i em u v simple machines

2,126 views

Published on

simple machines

Published in: Education
  • Be the first to comment

  • Be the first to like this

Diploma i em u v simple machines

  1. 1. . . Simple Machines Course :- Diploma Engineering Sub :- Engineering Mechanics Unit :- V
  2. 2. Laws of Motion • Concept of momentum • In classical mechanics, linear momentum or translational momentum is the product of the mass and velocity of an object. • For example, a heavy truck moving fast has a large momentum—it takes a large and prolonged force to get the truck up to this speed. If the truck were lighter, or moving more slowly, then it would have less momentum. • Like velocity, linear momentum is a vector quantity, possessing a direction as well as a magnitude: • Ρ = mv
  3. 3. Newton’s Laws of Motion • Newton's First Law of Motion: • Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. • Newton's Second Law of Motion: • The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. • Newton's Third Law of Motion: • For every action there is an equal and opposite reaction.
  4. 4. Application • Applications of Newton's First Law • Blood rushes from your head to your feet while quickly stopping when riding on a descending elevator. • The head of a hammer can be tightened onto the wooden handle by banging the bottom of the handle against a hard surface. • A brick is painlessly broken over the hand of a physics teacher by slamming it with a hammer.
  5. 5. Application • Applications of Newton's Second Law • An apple falling to the ground must be under the influence of a force, according to his second law. That force is gravity, which causes the apple to accelerate toward Earth's center. • Applications of Newton's third Law • Newton reasoned that the moon might be under the influence of Earth's gravity, as well, but he had to explain why the moon didn't fall into Earth. Unlike the falling apple, it moved parallel to Earth's surface.
  6. 6. Derivation Of Force Equation From Second Law Of Motion • The second law states that the net force on an object is equal to the rate of change (that is, the derivative) of its linear momentum p in an inertial reference frame: F = dp / dt • The second law can also be stated in terms of an object's acceleration. Since the law is valid only for constant-mass systems, the mass can be taken outside the differentiation operator by the constant factor rule in differentiation.
  7. 7. Piles, Lifts, Bodies Tied with String • Piles • The response of a laterally loaded pile within a group of closely spaced piles is often substantially different than a single isolated pile. This difference is attributed to the following three items: 1. The rotational restraint at the pile cap connection. The greater the rotational restraint, the smaller the deflection caused by a given lateral load. 2. The additional lateral resistance provided by the pile cap. verifying and quantifying the cap resistance is the primary focus of this research.
  8. 8. • 3. The interference that occurs between adjacent piles through the supporting soil. Interference between zones of influence causes a pile within a group to deflect more than a single isolated pile, as a result of pile-soil-pile interaction. • Lifts Lifting Functions Attachments: Chains Cables Ropes Webbing
  9. 9. • Locations of attachment should be: • Directly over/in alignment with the load's center of gravity (CG). • Above the load's CG. • Bodies Tied With String • block of mass 2 kg sits on a frictionless ramp and is tied to the wall with a string as shown. The string is horizontal and tied to the center of the block. If the ramp is inclined at 20 degrees, what is the magnitude of the force from the block on the ramp?
  10. 10. Conservation of Momentum • The sum of moment of two objects remains same even after collision. • In other words, the sum of moments of two objects before collision and sum of moment of two objects after collision are equal.
  11. 11. Impulsive Force • The force that two colliding bodies exert on one another acts only for a short time, giving a brief but strong push. This force is called an impulsive force. • During the collision, the impulsive force is much stronger than any other forces that may be present; consequently, the impulsive force produces a large change in the motion while the other forces produce only small and insignificant changes. • For example, during the automobile collision shown in Figure, the only important force is the push of the wall on the front end of the automobile; the effects produced by gravity and by the friction force of the road during the collision are insignificant.
  12. 12. Simple Machine • Concept of machine • A machine is a tool that consists of one or more parts, and uses energy to meet a particular goal. • Machines are usually powered by mechanical, chemical, thermal, or electrical means, and are often motorized. Historically, a power tool also required moving parts to classify as a machine. • However, the advent of electronics technology has led to the development of power tools without moving parts that are considered machines.
  13. 13. Mechanical Advantage • Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply • trades off forces against movement to obtain a desired amplification in the output force. • Machine components designed to manage forces and movement in this way are called mechanisms. • An ideal mechanism transmits power without adding to or subtracting from it. This means the ideal mechanism does not include a power source, and is frictionless and constructed from rigid bodies that do not deflect or wear.
  14. 14. Mechanical Advantage • A simple machine has an applied force that works against a load force. If there are no friction losses, the work done on the load is equal to the work done by the applied force. This allows an increase in the output force at the cost of a proportional decrease in the distance moved by the load. • The ratio of the output force to the input force is the mechanical advantage of the machine. • If the simple machine does not dissipate or absorb energy, then its mechanical advantage can be calculated from the machine's geometry.
  15. 15. Velocity Ratio and Efficiency of A Machine • Speed ratio • The requirement for power input to an ideal mechanism to equal power output provides a simple way to compute mechanical advantage from the input-output speed ratio of the system. • The power input to a gear train with a torque TA applied to the drive pulley which rotates at an angular velocity of ωA is P=TAωA
  16. 16. • Efficiency • Mechanical advantage that is computed using the assumption that no power is lost through deflection, friction and wear of a machine is the maximum performance that can be achieved. • For this reason, it is often called the ideal mechanical advantage (IMA). In operation deflection, friction and wear will reduce the mechanical advantage. • The amount of this reduction from the ideal to the actual mechanical advantage (AMA) is defined by a factor called efficiency which is determined by experimentation.
  17. 17. Law Of Machine • Machines which are used to lift a load are governed by the "Law of machines", which states that the effort to be applied on the machine (p) is related to the weight (w) which it can lift as – p = mw + c • Where m and c are positive constants which are characteristics of the machine.
  18. 18. Simple Machines • Lever • A lever is a machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum. • It is one of the six simple machines identified by Renaissance scientists. The word comes from the French lever, "to raise", relevant. • A lever amplifies an input force to provide a greater output force, which is said to provide leverage. The ratio of the output force to the input force is the ideal mechanical advantage of the lever.
  19. 19. • The law of the lever • The lever is a movable bar that pivots on a fulcrum attached to or positioned on or across a fixed point. The lever operates by applying forces at different distances from the fulcrum, or pivot. 1
  20. 20. • Wheel And Axle • The wheel and axle is one of six simple machines identified by Renaissance scientists drawing from Greek texts on technology. • The wheel and axle is generally considered to be a wheel attached to an axle so that these two parts rotate together in which a force is transferred from one to the other. • In this configuration a hinge, or bearing, supports the rotation of the axle.
  21. 21. • Pulleys • A pulley is a wheel on an axle that is designed to support movement of a cable or belt along its circumference. • Pulleys are used in a variety of ways to lift loads, apply forces, and to transmit power. 2
  22. 22. • A pulley is also called a sheave or drum and may have a groove between two flanges around its circumference. • The drive element of a pulley system can be a rope, cable, belt, or chain that runs over the pulley inside the groove.
  23. 23. • Jacks Winch Crabs • Fitted with heavy cast iron wall brackets. The grooved wheel is of 25 cm diameter and gears are machine cut. • This apparatus is used for experiments in efficiency of mechanical advantage. Weights are not included. 3
  24. 24. IMAGE REFERENCES Sr. No. Source/Links 1 2 3 http://upload.wikimedia.org/wikipedia/commons/c/c3/L ever_Principle_3D.png https://encrypted- tbn3.gstatic.com/images?q=tbn:ANd9GcQR22SzbNS32UkJWWtVyJ zwF8-_JL2ljrKPQ8yAeWs5cpe_xUEhAFZkbVRh http://2.imimg.com/data2/WR/XP/MY-3735131/winch-crab- double-purchase-250x250.jpg
  25. 25. CONTENT REFERENCES  A TEXT BOOK OF ENGINEERING MECHANICS , R.S.KHURMI , S.CHAND & COMPANY PVT. LTD. A TEXT BOOK OF ENGINEERING MECHANICS , Dr. R.K.BANSAL , LAXMI PUBLICATION
  26. 26. Any Question??
  27. 27. Thank You

×