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Note on Lever

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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.

  • 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.
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Very Short Questions

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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  • In first class lever ______.

    none of these


    load is between the effort and fulcrum


    effort is between the load and the fulcrum


    fulcrum lies anywhere between the effort and load


  • Bottle opener is an example of ______.

    Third class Lever


    First Class Lever


    Second class Lever


    both b and c


  • The effort arm of a lever is 4m long and the load arm is 2m long. What is the effort required to lift a load of 40N?

    15 N


    30 N


    25 N


    20N


  • The part of lever that carries the load is called ______.

    load arm


    effort arm


    force arm


    fulcrum


  • The part of lever where effort is applied is called ______.

    load arm


    fulcrum


    effort arm


    effort arm


  • The components of a lever are _____.

    load


    load arm


    effort


    all of the above


  • The component of a lever which lets the bar to move freely in an axis is called ______.

    effort arm


    fulcrum


    effort


    load arm


  • Which of the following is a first class lever?

    crow-bar


    scissors


    see-saw


    all of the above


  • Which of the following is not the first class lever?

    wheel barrow


    see-saw


    all of the above


    crow-bar


  • For a lever to be a first class lever which component has to be in the middle?

    effort arm
    effort
    load
    Fulcrum
  • In first class lever ______.

    effort arm is longer than load arm


    load arm is longer than effort arm


    effort arm is equal to the load arm


    effort arm is shorter than load arm


  • In second class lever ______.

    effort arm is shorter than load arm


    load arm is longer than effort arm


    effort arm is longer than load arm


    effort arm is equal to the load arm


  • In third class lever ______.

    effort arm is longer than load arm


    effort arm is equal to the load arm


    load arm is shorter than effort arm


    effort arm is shorter than load arm


  • The lever in equilibrium state is defined by the equation ______.

    load x load arm = effort x effort arm


    load + load arm = effort + effort arm


    load / load arm = effort / effort arm


    load - load arm = effort - effort arm


  • For a lever to be a second class lever which component has to be in the middle?

    effort
    fulcrum
    load
    effort arm
  • Which one of the following is not a second class lever?

    wheel barrow


    handle of the water pump


    nut cracker


    lemon squeezer


  • For a lever to be a third class lever which component has to be in the middle?

    load
    effort
    fulcrum
    effort arm
  • In a first class lever if we want to gain more force the position of fulcrum should be ______.

    anywhere in between. The position of fulcrum doesn't matter.


    in exact middle of the load and the effort


    closer to the load


    closer to the effort


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DISCUSSIONS ABOUT THIS NOTE

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Forum Time Replies Report
Akku

What do you mean by MAof a lever is 3?


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sachin

A second class lever need less effort to lift a heavy load,why?


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111

how does simple machine help to change the direction of force??


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ink

isn't effort arm shorter than or longer than or equal to load arm??


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