Introduction to Simple machine:
A machine makes possible to overcome a big resistance or load by applying a small effect. A machine let us to do work more effortlessly and easily than could be done without it. Its main aim is to apply force on an object that is generally exerted to the machine. At times the force which the machine applies is in a dissimilar direction from that of the applied force.
Define: A machine is a tool or device that allows a force (or effort) applied at one point to overcome a resisting force (or load) at the other point. Illustration: The lever, nut-crackers, pulleys, pliers, wedge, wheelbarrows, wheel and axle, inclined plane, screw jack and countless others.
Force ratio or mechanical advantage:
We state efforts as the force applied to a machine and load as the force or resistance overcome through the machine. The capability of a machine to overcome a large load via a small effect is observe as Force Ratio or Mechanical Advantage (MA). This is given by:
MA = Load/Effort
Mechanical Advantage or Force Ratio = Output force/Input force
Velocity Ratio (VR):
We state Velocity Ratio (VR) as the ratio of the distance moved through the effort and the load in the time interval.
VR = distance moved by effort (e)/distance moved by load (l)
The Velocity Ratio mainly based on the geometry of the machine. This is independent of the friction. For an ideal machine, that is, a machine which consists of no friction, as well termed as perfect machine, worked done by machine = work done on machine.
Thus, Load distance moved by load = effort × distance moved by effort.
Load/effort = distance moved by effort (e)/distance moved by load (l)
Load/effort = Velocity Ratio
We state the Efficiency (Ef) of a machine as:
Ef = Useful work done by the machine/Work put into the machine × 100%
Relationship between Mechanical Advantage (Force Ratio), Velocity Ratio and Efficiency:
Efficiency = Work done on the load/Work done by the effort
As the effort does the work on the machine and the load is worked on by the machine, efficiency can as well be represented as:
Efficiency = Work got out of machine/Work put into the machine = Output energy/Input Energy
Or, Efficiency = (Load x distance moved by load) / (Effort x distance moved by effort)
Efficiency = (Load/Effort) x (distance moved by load/ distance moved by effort)
Efficiency = (Load/Effort) / (distance moved by effort/distance moved by effort)
However, M.A. = (Load/Effort) and V.R. = (Distance through which effort acts) / (Distance moved by load)
Thus, Efficiency = (Mechanical advantage) / (Velocity ratio)
The efficiency is much frequently represented as a percentage, that is,
Efficiency = (M.A. /V.R.) x 100
Fundamental information of simple machines:
Simple machines make work simpler by reducing, multiplying or changing the direction of a force. The logical formula for work is w = f x d or, work is equivalent to force multiplied by distance. Simple machines can't change the amount of work done, however they can decrease the effort force which is needed to do the work!
There are mainly six kinds of simple machines: pulleys, wheels and axles, inclined planes, levers, wedges and screws.
Levers are a board or bar which turn on a fixed support termed as a fulcrum. Levers increase and lower an object as force is applied on the lever. An illustration of a lever is a bottle-opener: the handle acts as a lever arm and the pivot which fits beneath the rim of the cap acts as a fulcrum. A light switch, garage gate, scissors, broom, toaster handle, oven or refrigerator door are illustrations of a lever.
There are basically three types of levers:
First Class Lever: If the fulcrum lies between the force arm and the lever arm, the lever is illustrated as a first class lever. However, most of us are well-known with this kind of lever. It is the classic teeter-totter instance.
Second Class Lever: In this kind of class lever, the load arm lies between the fulcrum and the force arm. A good illustration of this kind of lever is the wheel-barrow.
Third Class Lever: In this kind of levers, the force arm lies between the fulcrum and the load arm. Due to this arrangement, a relatively large force is needed to move the load. This is offset by the fact that it is possible to produce the movement of the load over a long distance by a relatively small movement of the force arm. Fishing rod is a good example of it.
2) Inclined plane:
An inclined plane is a flat surface or board set at an angle to the horizontal. As the force required to push an object up an inclined plane is less than the force required to lift the similar object, inclined planes decrease the amount of force essential to do a job. A ramp is an illustration of an inclined plane. The illustrations comprise: Roller coaster, sloping roads, stirs, ramps, boat propeller and so on.
A pulley is a wheel having a grooved rim which is employed to decrease the amount of force and change the direction of force requires to do work. Pulleys are altered levers; their fulcrum is at their center. A fixed pulley is employed to change the direction of force required to do work; in order to hoist up a load having a pulley and rope, force is applied downward on the rope. As it is simpler to pull down by using your own weight than to pull upwards, fixed pulleys are generally employed. A moveable pulley is joined to a load and is employed to decrease the amount of force required to do work. It slides all along a rope, instead of a rope sliding all along it. A block and tackle is a combination of fixed and moveable pulleys, and is employed to both modifies the direction and the amount of the force required to do work.
Illustrations comprise: Elevator, Flag post, Crane, Window blinds and Winch.
4) Wheel and Axle:
The wheel and axle is a type of lever which moves objects across distances. The axle is a rod which goes via the wheel. This lets the wheel turn. The wheels of a car or bicycle are wheels and axles that allow the car or bicycle to move simply via it is a heavy object. Roller skates, gears in clocks or watches are as well illustrations of wheel and axles.
A screw is a simple machine which consists of a cylinder looking body having one or more ribs around it. The ribs are similar to the inclined planes wrapped around the cylinder. The screw lets objects to hang of the screw easily. The screw will stay secure in one place. The more ribs the stronger and more weight it can hold. Illustrations comprise: Drills, Screw lid jar, door lock, meat grinder, brace and bits.
A wedge is a kind of simple machine having a both a thin and sharp end and a thick and smooth end. This is in the shape of a triangular prism, or often explained as two inclined planes which are stuck back to back. There is less force required if driving a thin wedge via a surface than a bigger one however the thin wedge requires to be driven a bigger distance, therefore the work must be regarding the same. The illustrations comprise the Knives, axe, pin, forks, chisels and so on.
Effect of Friction on Simple Machines and Methods of Reduction:
The existence of friction among the moving parts of machines makes it unfeasible for any machine to encompass an efficiency of 100%. This is because part of the effort exerted is employed to overcome the frictional forces and the remainder is used to do helpful work. The work done in overcoming friction is useless or wasted energy and it appears as heat in the moving portions of machines.
In order to enhance the efficiency of machines you will try to decrease the friction present between the moving portions of the machine by:
1) Lubricating that prevents metal surfaces from rubbing against one other.
2) Utilizing ball bearings or roller bearings between the two surfaces in contact.
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