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MECHANICAL
ADVANTAGE OF LEVER
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| Consider the example of a lever of 1st kind. | |||
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| In
equilibrium position torque of effort is always equal to the torque of load. I.e. |
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Clockwise
torque = Anti clockwise torque
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Torque
of effort = torque of load
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| OR | |||
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effort
x effort arm = weight x weight arm
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P
x OA = W x OB
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OA
= W x OB/P
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W/P
= OA/OB
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but
[W/P = M.A.]
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M.A
= OA/OB
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| OR | |||
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M.A.
= Effort arm / weight arm
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| This equation shows that mechanical advantage of lever can be increased: | |||
By increasing effort arm. By
decreasing weight arm |
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| For latest information , free computer courses and high impact notes visit : www.citycollegiate.com | |||
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PULLEY
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| 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. | |||
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FIXED
PULLEY
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| 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”. | |||
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MECHANICAL
ADVANTAGE
OF FIXED PULLEY |
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| 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 : | |||
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effort
= load
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P
= W
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Dividing
both sides by P
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P/P
= W/P
W/P = 1 |
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Since
[W/P = M.A]
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M.A
= 1
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| This shows that fixed pulley can only change the direction of force but it will lift load equal to the effort applied on it. | |||
| For latest information , free computer courses and high impact notes visit : www.citycollegiate.com | |||