Class 6 Simple Machines MCQ with Answers

MCQs and Mock Test | NCERT - CBSE Curriculum

Practice Class 6 Simple Machines MCQs.
Learn about levers, pulleys, inclined planes, wedges, screws, wheel and axle, mechanical advantage, and efficiency - with instant answers and performance report.

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Quick Revision: Simple Machines

  • Work: Done only when a force applied on a body moves it. No motion = no work (S.I. unit: Joule).
  • Energy: The capacity of a body to do work (S.I. unit: Joule).
  • Machine: A device that helps us do work more easily by applying less force and spending less energy.
  • Effort (E): The force applied on a machine.
  • Load (L): The object that a machine lifts or moves.
  • Mechanical Advantage (M.A.): Ratio of Load to Effort (M.A. = L / E).
  • Efficiency: Ratio of useful work output to work input. Ideal machine = 100% efficient. Actual machines are less than 100% due to friction.
  • Six Simple Machines: Lever, Pulley, Wheel and Axle, Inclined Plane, Wedge, Screw.
  • Lever: A rod that turns about a fixed point called the fulcrum. Has load arm and effort arm. M.A. = Effort arm / Load arm.
  • Class I Lever: Fulcrum between load and effort (e.g., see-saw, scissors).
  • Class II Lever: Load between fulcrum and effort (e.g., nutcracker, wheelbarrow). Always a force multiplier (M.A. > 1).
  • Class III Lever: Effort between fulcrum and load (e.g., sugar tongs, forearm). Always a speed multiplier (M.A. < 1).
  • Pulley: A grooved wheel that turns about an axle. Used to change the direction of effort.
  • Inclined Plane: A sloping surface used to move heavy loads with less effort. M.A. = Length of slope / Height.
  • Wedge: Two inclined planes joined back-to-back to form a sharp edge (e.g., axe, knife).
  • Screw: An inclined plane wound around a rod (e.g., screw jack).
  • Wheel and Axle: A wheel attached to an axle (e.g., screwdriver, bicycle pedal).
  • Friction: Reduces efficiency of machines. Lubrication reduces friction and increases efficiency.

Simple Machines Class 6 Questions and Answers (FAQ)

What are simple machines and why are they used in Class 6 Science?
Simple machines are basic devices that help us do work more easily by applying less force or by changing the direction of force. The six simple machines are the lever, pulley, wheel and axle, inclined plane, wedge, and screw. They are used to multiply force, multiply speed, change the direction of effort, or change the point of application of effort.
What is the difference between Class I, Class II, and Class III levers?
Levers are classified based on the position of the fulcrum, load, and effort. Class I levers have the fulcrum between the load and effort (e.g., see-saw, scissors). Class II levers have the load between the fulcrum and effort (e.g., nutcracker, wheelbarrow) and are always force multipliers. Class III levers have the effort between the fulcrum and load (e.g., sugar tongs, forearm) and are always speed multipliers.
What is mechanical advantage and how is it calculated?
Mechanical Advantage (M.A.) is the factor by which a machine multiplies the force applied. It is calculated as the ratio of the load to the effort (M.A. = Load / Effort). For a lever, it is also the ratio of the effort arm to the load arm. If M.A. > 1, the machine is a force multiplier. If M.A. < 1, it is a speed multiplier.
Why is no machine 100% efficient and how can efficiency be improved?
No machine is 100% efficient because some work is always wasted in overcoming friction between moving parts. Efficiency is the ratio of work output to work input. Friction reduces efficiency. To improve efficiency, we can reduce friction by lubricating moving parts, polishing surfaces, and using ball bearings. Proper maintenance also increases a machine's life span and efficiency.
What is the difference between a wedge and an inclined plane?
An inclined plane is a single sloping surface used to move heavy loads up with less effort (e.g., a ramp). A wedge is a simple machine with a sharp edge formed by joining two inclined planes together (e.g., axe, knife). While an inclined plane is stationary and the load moves, a wedge moves and is driven into an object to split or cut it.

Chapter Summary: Simple Machines

Simple machines are devices that make work easier by allowing us to apply less force over a greater distance or by changing the direction of force. The six basic simple machines are the lever, pulley, wheel and axle, inclined plane, wedge, and screw. The lever is a rod that turns about a fixed point called the fulcrum. Levers are classified into three types based on the positions of the fulcrum, load, and effort. Class I levers (fulcrum in the middle) can multiply force or speed. Class II levers (load in the middle) are always force multipliers. Class III levers (effort in the middle) are speed multipliers.

Mechanical Advantage (M.A.) is the ratio of the load to the effort. For a lever, M.A. is also the ratio of the effort arm to the load arm. Efficiency is the ratio of useful work output to work input. No real machine is 100% efficient because some work is wasted overcoming friction. Proper lubrication reduces friction, increasing a machine's efficiency and lifespan. Understanding simple machines helps us appreciate how they are used in everyday tools and complex machinery.

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