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How to calculate Mechanical Advantage of a Lever?


Mechanical Advantage of a Lever

Here in this post we discuss on the definition of lever (what is lever in Physics), types of lever, Mechanical Advantage of levers, the Effort arm, Load arm for different types of lever and equilibrium of lever.

Lever

A lever is a simple machine which is basically a rigid rod which can rotate on a point on itself. That point or pivot is called Fulcrum (F). A lever is used to lift a load (L) by applying a force or effort (E).

Effort Arm: The length between Effort and Fulcrum = EA

Load Arm: the length between Load and Fulcrum = LA

Types of levers

On the basis of the location of fulcrum, load and effort, the lever is divided into 3 types.

Class I (Fulcrum in the middle) – example: seesaw where the pivot is in the middle.

 Class II (Load in the middle) – example: nutcracker where the nut (load here) is in the middle.

 Class III (Effort in the middle) – example: tweezers where effort is applied in the middle.

Mechanical Advantage of a Lever

A lever provides leverage to its users by amplifying the applied force or by providing comfort or convenience to do some specific activities.

Mechanical Advantage is the amplification factor of a lever. It’s the ratio of Load and Effort.

Mechanical Advantage of a lever =Load lifted/Effort applied= L/E _________(a)

In balanced or equilibrium of a lever, the following condition is satisfied.

LA * L = EA * E

i.e., Load Arm X Load = Effort Arm X Effort__________(b)

or Load / Effort = Effort Arm / Load Arm…………………………….(c)

As we know, Mechanical Advantage = Load/Effort

that means, another expression of Mechanical Advantage is obtained here.

i.e. from equation (c) above,

Mechanical Advantage of lever = load / effort

= Effort Arm / Load Arm = EA /LA

So its clear that to leverage a lever and get mechanical advantage value more than 1,  EA should be more than LA. This means the load should be nearer to the fulcrum (to have a smaller Load Arm) and the Effort should be applied farther from the fulcrum (to make the Effort Arm larger).

For class I and II levers, we can get mechanical advantage more than 1 by following the above said condition. Now remember that, Mechanical Advantage = Load/effort. So making Mechanical Advantage more than 1 means Load lifted is more than the Effort Applied. Thus the effort is multiplied and a load more than the applied Effort can be lifted by a lever.

In class III lever Mechanical Advantage can never be equal or more than 1. Can you say why?

Contd:

 

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