Notes on Lever | Grade 8 > Science > Simple Machine | KULLABS.COM

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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.
.

### 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 ______.

load is between the effort and fulcrum

none of these

fulcrum lies anywhere between the effort and load

effort is between the load and the fulcrum

• ### Bottle opener is an example of ______.

Third class Lever

both b and c

Second class Lever

First Class Lever

20N

15 N

25 N

30 N

force arm

fulcrum

effort arm

effort arm

effort arm

fulcrum

• ### The components of a lever are _____.

effort

all of the above

effort arm

fulcrum

effort

• ### Which of the following is a first class lever?

all of the above

scissors

see-saw

crow-bar

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

all of the above

crow-bar

see-saw

wheel barrow

effort arm
effort
Fulcrum
• ### In first 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 second class lever ______.

effort arm is longer than load arm

effort arm is equal to the load arm

effort arm is shorter than load arm

load arm is longer than effort arm

• ### In third class lever ______.

load arm is shorter than effort arm

effort arm is equal to the load arm

effort arm is longer than load 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

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

lemon squeezer

nut cracker

wheel barrow

handle of the water pump

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

in exact middle of the load and the effort

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

closer to the load

closer to the effort

## ASK ANY QUESTION ON Lever

Forum Time Replies Report
##### Akku

What do you mean by MAof a lever is 3?

##### sachin

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

##### 111

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