Wheel and axle

Wheel and axle
The type of simple machine which consist of two co-axial cylinders of different diameters which a mounted on the axle.
  
Diameter

A diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle.  


Radius 
Radius  is a line segment from the center to the perimeter (surrounding area) of a circle. Half of a diameter is the length of radius.


In wheel and axle radius is the effort distance.
Radius of wheel is denoted by capital r "R" where as radius of axle is denoted by small r "r".


# Generally effort is applied in a big cylinder and load is applied on a small cylinder which means ED  is greater than LD.

Mathematically,
VR = ED 
         LD
      =  Radius of wheel 
          Radius of axle
       =   R 
            r 
Therefore VR of wheel and axle is =   R 

                                                              r  

We know radius of wheel is greater than the radius of axle which makes the VR greater than 1 and more easy by magnification of force.

Types of Simple Machine

Types of Simple Machine
There are Six types of lever. They are:- 
1) Lever                                 4) Inclined Plane
2) Pulley                                5) Screw
3) Wheel and axle                  6) Wedge


Lever
Lever is a rigid bar which is capable to rotate a fixed point called fulcrum.


Rembemer:- If the effort distance is greater than load distance magnification of force is there and the work can be done easily 


Fulcrum is denoted as Δ , load as ¨ effort as $or# in the figure.
There are three types of lever. They are:-
1) First class lever
2) Second class lever
3) Third class lever 


First class lever
The lever in which fulcrum is between load and effort is called first class lever.

In First class lever 
Ld < Ed
Ld > Ed
Ld = Ed
Ld ≠ Ed


Second class lever
The type of lever in which load is in between fulcrum and effort. 

In Second class lever Ed is always greater than load distance which magnification of force and make our work easier.


Third class lever
The type of lever in which effort is between fulcrum and load.

In Third class lever Ld is always greater than Ed in which there is no magnification of force and makes our work more difficult. MA of Third class lever is less than 1.

Ratio defination and formula

Mechanical Advantage (MA)
Mechanical Advantage of a machine is defined as a ratio of a load overcome by the machine to the effort applied in the machine.
Mathematically,
                           MA=    load   
                                       effort 
            i.e            MA=    L   

                                        E

It has no unit as it is the ratio of  two force.

What is meant by a simple machine having MA3?

It meant that we can overcome the load of 3 Newton (N)  by applying the effort of 1N using simple machine. 


Velocity Ratio (VR)
Velocity Ratio is defined as a  ratio of effort distance to load distance.

Mathematically,

                            VR=    effort distance   

                                        load distance 

            i.e             VR=    ED   

                                         LD

Efficiency

It is the ratio of work output to work input per 100%.

Mathematically,

                 Efficiency=    Work output  

                                        Work Input 

                                 = L Í LD 

                                    E Í ED

         =  L  Í  LD 

                                     E       ED 

         =   L    ÷ ED 

                                         E       LD                             

                                                 =  MA ÷ VR 
                                 =   MA 
                                       VR

           i.e   Efficiency=   MA 
                                        VR


                                        

Important Question

Rest and Motion are relative terms . Why?
Rest and motion are relative terms because if we suppose a tree on the roadside.It is the state of rest as it is not changing its position with respect to a moving car but a car changes it position with respect to the tree. As,it is the state of motion, Therefore the treee is at rest but the running car is in motion relative to the tree. Hence rest and motion are relative terms.

Difference Between

Difference between scalar and vector quantity

Scalar	Vector
The quantities that have magnitude but no direction is called scalar quantity.	The quantities that have both magnitude and direction is called scalar quantity.
It is denoted by ‘A’	It is   represented by arrow head  with
It is measured by certain degebric matter.	It is added by certain vactor rule.
Sum of scalar quantity is always positive	Sum of scalar quantity can be positive, negative or zero