MECHANICAL ADVANTAGE OF LEVER
 
 
Consider the example of a lever of 1st kind.
In equilibrium position torque of effort is always equal to the torque of load.
I.e.
Clockwise torque = Anti clockwise torque
Torque of effort = torque of load
OR
effort x effort arm = weight x weight arm
P x OA = W x OB
OA = W x OB/P
W/P = OA/OB
but [W/P = M.A.]
M.A = OA/OB
OR
M.A. = Effort arm / weight arm
This equation shows that mechanical advantage of lever can be increased:
By increasing effort arm.
By decreasing weight arm
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PULLEY
A pulley is a simple machine. It consists of a wheel mounted on an axis which is fixed to a frame called block. The wheel is free to rotate. With the help of pulley we can lift heavy loads very easily by applying little force and also change the direction of force.
FIXED PULLEY
If the block of the pulley is fixed to a strong beam or ceiling, the pulley will not move and is called a “Fixed Pulley”.
MECHANICAL ADVANTAGE
OF FIXED PULLEY
In fixed pulley, the effort ‘P’ is applied which is equal to the load ‘W’, if we ignore weight of rope and force of friction between rope and pulley then :
effort = load
P = W
Dividing both sides by P
P/P = W/P
W/P = 1
Since [W/P = M.A]
M.A = 1
This shows that fixed pulley can only change the direction of force but it will lift load equal to the effort applied on it.
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