Levers and Simple Machines MCQ Quiz - Objective Question with Answer for Levers and Simple Machines - Download Free PDF

Concept:

• A lever is a rigid rod which rotates about a fixed point called the fulcrum.
• All levers are functioning on the following principle:
• Load × Load arm = Effort × Effort arm
• The distance of the load from the fulcrum is called the load arm and the distance of the effort from the fulcrum is called effort arm.

Key Points

Straight levers are classified as:

Thus, in third class lever, the force is in between weight and fulcrum.

Explanation:

Mechanical Advantage: 

• In a simple machine when the effort(P) balances a load (W), the ratio of the load to the effort is called MA.
• \(M.A = \frac{{Load}}{{Effort}} = \frac{W}{P}\)

Velocity Ratio: 

• It is the ratio between the distance moved by the effort to the distance moved by the load.
• \(V.R = \frac{{distance\;moved\;by\;the\;effort\;\left( {{d_P}} \right)}}{{distance\;moved\;by\;the\;load\;\left( {{d_w}} \right)}}\)

Efficiency: 

• It is the ratio of output to input. In a simple mechanism, it is also defined as the ratio of mechanical advantage to the velocity ratio.
• \(\eta = \frac{{Output}}{{Input}} = \frac{{M.A}}{{V.R}}\)
• In actual machines, a mechanical advantage is less than the velocity ratio
• In an ideal machine, the mechanical advantage is equal to the velocity ratio.

Explanation:

• Levers are simple machines consisting of a rigid bar that pivots around a fixed point called the fulcrum.
• The three classes of levers, designated as Class 1, Class 2, and Class 3, are categorized based on the relative positions of the fulcrum, the applied force (effort), and the resistance (load). 

Class 1 Lever:

• Arrangement: The fulcrum is placed between the effort and the load.
• Examples: Seesaw, crowbar, scissors.

Class 2 Lever:

• Arrangement: The load is between the fulcrum and the effort.
• Mechanical Advantage: The load arm is always longer than the effort arm, providing a mechanical advantage.
• Examples: Wheelbarrow, nutcracker.

Class 3 Lever:

• Arrangement: Effort is between the fulcrum and the load.
• Mechanical Advantage: The effort arm is always shorter than the load arm, providing a mechanical disadvantage.
• Examples: Human arm (elbow joint), tweezers.

Explanation:

The correct expression to find the effort lost in actual machines due to friction compared to ideal lifting machines is given by:

=\(\frac{W}{V \cdot R \cdot}\left(\frac{1}{\eta}-1\right)\)

where, 

W = load

V. R. = velocity ratio of the machine

 η = efficiency of the machine

Additional InformationMechanical Advantage:

• In a simple machine when the effort(P) balances a load (W), the ratio of the load to the effort is called MA.
• \(MA=\frac{Load}{Effort}= \frac {W}{P}\)

Velocity Ratio:

• It is the ratio between the distance moved by the effort to the distance moved by the load distance.
• \(V.R. = \frac {distance moved by the effort (d_p)}{distance moved by the load (d_w)}\)

Efficiency:

• It is the ratio of output to input. In a simple mechanism, it is also defined as the ratio of mechanical advantage to the velocity ratio.
• \(\eta=\frac{Output}{Input}=\frac{M.A.}{V.R.}\)

Explanation:

Levers

• A lever is a rigid bar (straight, curved, or bent) and is hinged at one point.
• It is free to rotate about the hinged end called a fulcrum.
• Common examples of the use of a lever are a crow bar, pair of scissors, fire tongs, etc.
• It may be noted that there is a point for effort (called effort arm) and another point for overcoming resistance or lifting load (called load arm).

Types of Levers

1. Simple levers
2. Compound levers

Simple levers

• A lever, which consists of one bar having one fulcrum is known as a "simple lever.
• Let, P = Effort applied, W = Weight lifted, a = Length between fulcrum and effort, and b = Length between fulcrum and weight.
• Now taking moments of the effort and load about the fulcrum (F) and equating the same.
• P .a = W.b or W/P = a/b
• The terms W/P and a/b are commonly known as mechanical advantage and leverage. A little consideration will show that in order to increase the mechanical advantage, either the length of the lever arm (a) is to be increased or the length of the load arm (b) is to be reduced.

Compound Lever

• A lever, which consists of a number of simple levers is known as a compound lever.
• A little consideration will show, that in a compound lever, the mechanical advantage (or leverage) is greater than that in a simple lever.
• Mathematically, Leverage in a compound lever = Leverage of 1st lever × Leverage of 2nd lever × ...
• The platform weighing machine is an important example of a compound lever.
• This machine is used for weighing heavy loads such as trucks, and wagons along with their contents.
• On smaller scales, these machines are used in godowns and parcel offices of transport companies for weighing consignment goods.

Explanation:

• A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum, used to transfer a force to a load and usually to provide a mechanical advantage.
• On the basis of the locations of fulcrum, load, and effort, the lever is divided into three types.
• First Class Lever:In a first-class lever, the fulcrum is located between the effort and the load. When force is applied to one end of the lever (effort arm), it causes the other end to move, exerting force on the load. Examples include seesaws, crowbars, and scissors.

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• Second-class lever: In a second-class lever, the load is located between the fulcrum and the effort. This means that the effort arm is always longer than the load arm. When force is applied to the effort arm, it causes the load to move. Examples include wheelbarrows, bottle openers, and nutcrackers.

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• Third-class lever: In a third-class lever, the effort is applied between the fulcrum and the load. This means that the load arm is always longer than the effort arm. While third-class levers don't provide a mechanical advantage like first and second-class levers, they allow for greater speed and range of motion. Examples include fishing rods, shovels, and tweezers.

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Explanation: 

If the removal of effort while lifting, results in lowering of the load, the machine is said to be reversible.

The machine is said to be self-locking if the load is not lowered on the removal of the effort.

Important Points

A lifting machine is reversible if its efficiency is greater than 50 per cent and self-locking if its efficiency is less than 50 per cent.

Key Points

• In Class 1 and Class 3 levers, the fulcrum or the force is located at one end, requiring support like a bearing or pivot to hold the beam in place.
• Class 1 lever has the fulcrum between the effort and the load (e.g., seesaw), which must be held with a pivot/bearing.
• Class 3 lever has the effort between the fulcrum and the load (e.g., tweezers), also requiring support to stabilize the beam.
• These types of levers need a fixed point or axis of rotation, which is typically provided by a bearing, hinge, or other support.
• Class 2 levers do not usually require a bearing to stabilize the beam in the same way, as the load lies between the effort and fulcrum (e.g., wheelbarrow).

Additional Information

• Class 1 Lever:
  • Fulcrum between load and effort.
  • Examples: Seesaw, scissors, crowbar.
  • Can multiply force or speed depending on fulcrum position.
• Class 2 Lever:
  • Load between effort and fulcrum.
  • Examples: Wheelbarrow, nutcracker.
  • Always multiplies force; mechanical advantage > 1.
• Class 3 Lever:
  • Effort between fulcrum and load.
  • Examples: Tweezers, tongs, human forearm.
  • Multiplies speed and distance; mechanical advantage < 1.
• Role of Bearings:
  • Bearings provide rotational support to the lever beam, minimizing friction.
  • Essential in systems where a stable pivot point is necessary.
• Mechanical Advantage:
  • Levers provide mechanical advantage by trading force for distance or vice versa.

Concept:

Levers:

• Levers are the most basic machines which are used to do some work with minimal effort.
• A lever amplifies an input force to provide a greater output force, which is said to provide leverage.
• Types: First class lever, second class lever, third class lever.

Class 1 levers:

• It is a very simple machine comprised of a beam placed upon a fulcrum.
• A load is placed onto one end of a beam, while an effort is directed onto the other end to counter the load.

• In a first-class lever, the effort (force) moves over a large distance to move the load a smaller distance, and the fulcrum is between the effort (force) and the load.
• Examples of first-class levers are pliers, scissors, a crowbar, a claw hammer, a see-saw, and a weighing balance.

Explanation:

• A Class 1 lever has the fulcrum placed between the effort and load.
• The movement of the load is in the opposite direction of the movement of the effort.
• This is the most common lever configuration.
• The effort in a class 1 lever is in one direction, and the load moves in the opposite direction.​

Additional Information

Second class lever:

• In this class of lever, the load is applied in between the fulcrum and the effort force.
• Examples: Wheelbarrow, Nutcracker, etc.

Third class lever:

• In this class of lever, the fulcrum is at the one end and the effort force is applied in between the fulcrum and load.
• Examples: Human arms, Tongs, tweezers, etc.
• It consists of two levers which works together.

Explanation:

Levers are classified into three types or class based on the position of load and effort on the fulcrum

Double Class 1 Lever:

• When we say that pliers and scissors are considered "double Class 1 levers," we refer to the fact that each tool consists of two lever arms working together around a common fulcrum.
• Pliers: Each handle and jaw can be viewed as a separate Class 1 lever. Both levers share the same fulcrum (the joint), and they work simultaneously to grip or cut.
• Scissors: Similarly, each blade and handle of the scissors acts as a separate Class 1 lever. The two levers pivot around the same fulcrum (the joint), working together to achieve the cutting action.
• Examples: Nutcracker, Bolt Cutters, Tin Snips/Shears etc.

Class 1 Lever:

• A Class 1 lever has the fulcrum placed between the effort and load.
• The movement of the load is in the opposite direction of the movement of the effort.
• E.g. crowbars, scissors, pliers, tin snips, and seesaws
• A pair of pliers and scissors are together considered as a double Class 1 lever.

Class 2 Lever

• A Class 2 lever has the load between the effort and the fulcrum.
• In this type of lever, the movement of the load is in the same direction as that of the effort.
• E.g. nutcrackers, wheelbarrows, doors, and bottle openers

Class 3 lever

• A Class 3 lever has the effort between the load and the fulcrum.
• Both the effort and load are in the same direction.
• E.g. tweezers, arm hammers, and shovels.

Explanation:

Lifting machines are those machines that are used for lifting loads. The force (or effort) is applied at one point of the machine and weight (or load) is lifted at the other point of the machine.

Pulleys used to lift water from a well and screw jacks used to lift buses are some of the common examples of lifting machines. 

Let P be the effort applied, W be the load lifted, y be the distance moved by the effort, x be the distance moved by the load. Then, 

• The input of machine = Py
• The output of machine = Wx 

Efficiency: It is the ratio of output to input. In a simple mechanism, it is also defined as the ratio of mechanical advantage to the velocity ratio.

\(η = \frac{{Output}}{{Input}} = \frac{{Wx}}{{Py}}=\frac{{\frac{{W}}{{P}}}}{{\frac{{y}}{{x}}}}=\frac{{\frac{{Load}}{{Effort}}}}{{\frac{{Dist.~moved~by~effort}}{{Dist.~moved~by~load}}}}\) = \(Mechanical ~advantage\over Velocity~ratio\)

Law of machine: It is the relation between the load lifted (W) and the effort applied (P). 

It is given by the equation:

P = m.W + C

where m = coefficient of friction which is equal to the slope of line AB in fig., C = constant represent machine friction

Maximum Mechanical Advantage: The maximum Mechanical Advantage of Lifting Machine is given by \(Max.MA=\frac{1}{m}\)

Explanation:

• A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum, used to transfer a force to a load and usually to provide a mechanical advantage.
• On the basis of the locations of fulcrum, load, and effort, the lever is divided into three types.

First Class Lever

• First-class levers have the fulcrum between the force and the load. 
• ​Effort and the load move in opposite directions.
• The effort in a class 1 lever is in one direction. 
• Examples: See-saw, crowbar, scissors, claw and hammers, the handle of water pump, a beam balance, wire cutter, plier, etc.

Second-class lever

• In second-class levers, the load is between the effort (force) and the fulcrum.
• Effort and the load moves in the same direction.
• Examples: Wheelbarrow, Staplers, Bottle openers, Nutcrackers, and Nail clippers.

Third-class lever

• In third-class levers, the effort is between the load and the fulcrum.
• Effort and the load moves in the same direction.​
• Examples: Fishing rod, Broom, Baseball bat, Bow and Arrow Human jaw.

Explanation:

Lever

• A lever is a rigid rod that rotates about a fixed point called the fulcrum.
• All levers are functioning on the following principle:
• Load × Load arm = Effort × Effort arm
• The distance of the load from the fulcrum is called the load arm and the distance of the effort from the fulcrum is called the effort arm.

Straight levers are classified as:

A simple machine is defined as a device, which is used in our daily life to make our work easier faster and more comfortable.

The Six Types of Simple Machines are:

Concept:

Lever:

• A lever is a simple machine made up of a rigid rod arranged in such a manner that it can move freely around a fixed part.
• It consists of the following three parts.

Fulcrum:

• This is the fixed point around which the rod moves.

Load:

• It is the object or weight on which work is to be performed.

Effort:

• It is the force that needs to be applied to the rod in order to perform a task.

Explanation:

On the basis of the position of load, effort, and fulcrum, the lever can be classified into three types.

First-class lever:

• The lever in which the fulcrum is located in between the load and the effort is called a first-class or class one lever.
• Examples: a pair of scissors, a see-saw, and a crowbar.

Second-class lever:

• A Lever in which the load is located between the fulcrum and the effort is called a second-class or class two lever.
• Examples: a wheelbarrow, a bottle opener, and a nutcracker.

Third-class lever:

• It is a Lever in which the effort is located in between the fulcrum and the load is called a third-class or class three lever.
• Examples: a stapler, a pair of tongs, and a finishing rod.

Levers of the third order.

• Levers in which the effort is situated between the load and the fulcrum are called levers of the third order.
• For example, a pair of tongs, the forearm of a person holding a load, a fishing rod, and a knife used to slice bread.
• The mechanical advantage of the levers of the third order is always less than one because their effort arms are shorter than their load arms.
• So, these machines can increase speed but cannot lift heavy loads, that is, a lever of the third order always reduces the force applied by the effort.

Hence, option-3 is correct