Simple machines

https://bulletprofitsmartlink.com/smart-link/66592/4Simple machine:-

Such a device, with the help of which can do more work in less time by applying a less force, is called an simple machine. Eit the help of these instruments, the work becomes simple;  Such as pulley jack, lever etc.

Power or effort:-
               
The force we exert on the machine to do the work is called Power or Effort, it is written by the letter P.

Load or weight :-

The force used by the machine to overcome the obstruction or resistance of the object is called load.  It is written by w.

Mechanical advantage:-

Mechanical advantage is the ratio of the load and power or effort taken by the machine.

 Mechanical advantage = load : effort

M.A. = load/ effort      =  W/P

Velocity ratio :-

Velocity ratio is the ratio of distance (D) traveled by machine effort (p) and distance (d) traveled by load (W).

V.R = 

distance traveled D by machine effort 

        distance traveled(d) by load 

V.R. =  D:d   = D/d 

Principle of machine :-

If we assume that there is no friction in the machine then the work done on the machine is equal to the work done by the machine.

That is,  work done = work taken

                 Input = output

                   P×D = W×d

 Efficiency of a machine η :- 

The ratio of output to the input of machine is known as efficiency. In simple machines, the ratio of mechanical advantage to the velocity ratio is also known as efficiency of machine. 

Efficiency is generallyexpressed in

percentage. 

Efficiency of machine η = output/input

         η  =  Mechanical advantage (M.A)

                        Velocity ratio (V.R.)

               =   W/P

                     D/d

         η % = M.A.   × 100

                     V.R.

Relationship between M.A ,V.R.,and η 

     M.A. = η × V.R.

  

      V.R.  =  M.A. 

                      η

Ideal Machine:-

In an ideal machine the mechanical advantage is equal to the velocity ratio. so, efficiency is 100% or unity.

Fulcrum :- 

It is a fixed point in the machine around which the machine rotates (F).

Classification of simple machines:-

• Lever

• Inclined plane

• Pulley 

• wheel and axle

• wedge

• Screw jack

• Gear

• Lever:- 
      A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum. A lever is a rigid body capable of rotating on a point on itself.

a) principle of Lever :-

Load × load arm = effort× effort arm

b) mechanical advantage of Lever :-
According to principle of Lever -

Load × load arm = effort× effort arm

Load/effort = effort arm/load arm

     W/P = BF/AF

C) On the basis of the locations of fulcrum, load and effort, the lever is divided into three types :-

1. First Class Lever :- In which fulcrum lies between load and the effort. example:- Handpump ,scissor ,
Beam scale, plier , see - saw etc.

2.   Second  Class Lever :- In which load lies between the fulcrum and the
effort.

example:- Nut crakers, Paper sheet cutter, Bottleopeners,  Lime squeezer, Wheel barrow,  etc.

3.   Third Class Lever :- In which effort lies between the fulcrum and the load.

example:- stapler ,Fishing rod , human force arm, forceps, broom, fire tongs, etc.

D) according to shape:-

       
Bellcranked levers (Curved levers):-

In addition to the above types of levers, two rods may be joined together at an angle to increase leverage without utilising much space. Such levers are cranked levers and the special form inwhich included angle is 90°, is called the bell cranked lever.
example:- clutch pedal, Motor cycle breaks system .

• Inclined plane:-
                  The inclined plane at any angle along the horizontal line is called the inclined plane.  Like to put heavy things at a little height, we also put strips etc. which is tilted.  In this way, objects can be easily mounted with less force.

            Weight (w) = mg
             Effort (P) = mg  sin θ

           M.A.= W/P = mg / mg  sinθ

                     = 1/ sinθ
  Situation 2
                   W = R cosθ
                    P = R  sinθ
          M.A. = W/P = Rcosθ / R sinθ

                     = Cotθ = 1/tanθ

• Pulley:- 

      Generally speaking, a pulley is a circle of wood or metal that is cut around the circumference and outwards, on which a rope or chain is wrapped, it revolves around its axis.  With the help of these, heavy weights can be lifted easily such as to put a sack while applying tube wells to draw water from wells, for heavy lifting in factories etc.

Types of Pulleys:-
   
 1. Fixed Pulley:-
                 
It consists of a single pulley which is fixed in a fixed frame and revolves around its axis.  The rope hanging through its circumference hangs weight on one end and power is applied on the other end.  In this, the distance traveled by weight and power is of the amount of one, which is equal to the length of the rope.

 2. Moveable Pulley:-
                               
In this, one end of the rope is tied to the hook and the other end passes over the moving pulley over the stationary pulley, on which the power is applied.  In this, the load is tied under the moving ring.  On applying power, the moving pulley and load rise together.  The load tries to go down, but the power holds it.  The value of power is the same everywhere.

 3. Pulley block and tackle:-
                                  
   This system consists of two blocks.  The top block is hung with a hook while the bottom block is movable.  The load hangs along the bottom block.  Both blocks are encased.  One end of the rope is tied with a hook at the bottom of the top block and the other end comes from the top of the top block of the top block, which is powered by the same rope because  Is used so every place has equal amounts of P.  The number of two gut pulleys may be the same and may also vary.
                                      

 4. Differential Pulley:-

          It consists of two pulleys of different diameters mounted on the same axle in a fixed frame and a third axle hanging down from which the load is carried.  Chains are used.

                              

• Wheel and axle:-
   
            In this type of arrangement, the wheel and axle are mounted on the same shaft and rotate in the same direction on rotation.  The diameter of the wheel is greater than the diameter of the spindle.  The power is applied to the end with a rope wrapped on the wheel and the load is hung on the end of the rope wrapped on the axis.

•  wedge :-
                 It consists of two solid inclined planes.  Such as ax, knife, chisel etc.

If the angle of wedge is θ
Than M.A. = W/P  = 1/ ( 2sinθ/2)
      P = 2W sin θ  /2


 •   Screw Jack:-
                   
  It is used to lift the load on a base.  Such as when changing tires of vehicles.  It operates on the principle of screw thread.  Its main body mold is made of iron.  There is a nut on the upper end of the body, through which a spindle passes.  There is a cap at the top of the spindle, which is mounted under the load.  There is a handle under the cap, with the help of which we lift the cap by rotating the spindle so that the load placed on the cap rises.
    L= handle or lever
    h = pitch of thread of spindle
    W = carry weight 
     P = effort or power
     Input = p×2πL
     Output = w × h
     Input = output

p×2πL = w ×h .           M.A.= W / P
W/P = 2πL / h.             V.R. = 2πL / h
Efficiency = M.A.  × 100
                       V.R.
    =         W × h   × 100
               p×2πL

 •  Gear wheel:-
                          The gears are a type of toothed wheel.  There are at least 2 gears in the same set and their teeth are the same size, the number of teeth in larger gears is more.  Smaller gears tend to have fewer teeth.

 For example, a bicycle has 2 gears which are connected by a continuous chain, the larger gear is called the driving gear and the smaller gear is driven gear. When applied the force rotates in the same direction.