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Lever

Subject: Science

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Overview

A lever is a simple machine. It consists of a rigid bar which is free to turn about a fixed point called fulcrum. There are three types of lever depending upon the position of load, effort and fulcrum. This note provides us with the information about lever, its use in practical life and types of lever with examples.
Lever

A lever is a simple machine. It consists of a rigid bar which is free to turn about a fixed point called fulcrum. The weight to be lifted is the load and the force applied to the bar is called effort. The distance of the load from the fulcrum is called the load arm and the distance of effort from the fulcrum is called the effort arm.

There are three types of lever depending upon the position of the load, effort, and fulcrum. These are

  1. First class lever
  2. Second class lever
  3. Third class lever

First class lever

A first class lever is one in which the fulcrum lies anywhere between the effort and load. Examples: Crowbar, seesaw, scissors, pliers, beam balance, the handle of water pump, etc.

Second class lever

A second-class lever is one in which the load is between the effort and fulcrum.

Examples: Wheelbarrow, nutcracker, bottle opener, oar of a rowboat, etc.

Third class lever

A third class lever is one in which the effort is between the load and the fulcrum

Examples: shovel, sugar tongs, finger nut cutter, tweezers, human forearm, fork, fishing rod, etc.

Things to remember
  • lever is a rigid bar, which is capable of rotating about a fixed point called fulcrum.
  • The types of lever are First class lever, Second class lever, Third class lever.
  • It includes every relationship which established among the people.
  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.
Videos for Lever
Levers
The Lever, a Simple Machine
Questions and Answers

A lever is a simple machine which consists of a rigid bar which is free to turn about a fixed point called fulcrum. The principle of lever is, the nearer the fulcrum to the weight to be moved, the easier it is to shift, the farther from the fulcrum, the more difficult.

Long spanner provides more effort arm and produces more turning effort.

Because effort arm is increased according to the principle of lever less effort is required.

Lever is divided into three types. They are: first class lever, second class lever and third class lever.

Solution,

\begin{align*} \text {Load}\: (L) = 40N\\ \text {Load arm}\: (L. d) = 2m\\ \text {Effort arm}\: (E.d) = 4m\\ \text {Effort} (E) =?\\ \text {According to the principle of lever,} \\ \text {Load} \times \text {Load arm} &= \text {Effort} \times \text {Effort arm} \\ \text {or,}\: 40 \times 2 = E \times 4 \\ \text {or,}\: 80/4 &= E \\ \text {or,}\: E = 20N \\ \text {Hence, the effort required to lift a load is}\: 20\:N. \\\end{align*}

Solution:

\begin{align*} \text {Load}\: (L) = 600N \\\text {Load arm}\: (L. d) = 0.5\\ \text {Effort arm}\: (E. d) = 1.5 - 0.5 m= 1m \\ \text {Effort}\: (E) =?\\ \text {According to the principle of lever,} \\ \text {Load} \times \text {Load arm} &= \text {Effort} \times \text {Effort arm} \\\text {or,}\: 600 \times 0.5 &= E \times 1 \\ \text {or,}\: E &= 300N \\ \text {Hence, the effort required to lift a load is}\: 300\:N. \\ \end{align*}

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