Skip to content
SmartScience
All Physics chapters

ICSE Class 10 · Physics · Chapter 3

Machines

6 topics · 15 questions

Smart summary

Everything you need, in order

Introduction to Machines

  • Machine: A device that makes work easier by changing the magnitude or direction of force.
  • Simple Machines: Lever, pulley, inclined plane, wheel and axle, wedge, and screw.
  • Purpose: Machines help multiply force, change direction of force, or gain speed.
  • Input and Output: Effort (input force) and Load (output force).
  • Real vs Ideal Machines: Real machines have friction and energy losses; ideal machines have 100% efficiency.

Mechanical Advantage (M.A.)

  • Definition: The ratio of load to effort. M.A. = Load/Effort.
  • Meaning: Indicates how many times a machine multiplies the effort force.
  • Unit: M.A. has no unit (it's a ratio).
  • M.A. > 1: Machine multiplies force (force multiplier).
  • M.A. < 1: Machine multiplies speed (speed multiplier).
  • M.A. = 1: Machine only changes direction of force.

Velocity Ratio (V.R.)

  • Definition: The ratio of the velocity of effort to the velocity of load. V.R. = Velocity of Effort / Velocity of Load.
  • Alternative Definition: V.R. = Distance moved by effort / Distance moved by load.
  • Characteristic: V.R. is constant for a given machine and depends only on its geometry.
  • Unit: V.R. has no unit (it's a ratio).
  • Ideal Machine: For an ideal machine, M.A. = V.R.

Efficiency (η)

  • Definition: The ratio of useful work output to total work input. η = (Work Output / Work Input) × 100%.
  • Formula: η = (M.A. / V.R.) × 100%.
  • Range: Efficiency is always less than 100% for real machines due to friction and other energy losses.
  • Factors Affecting Efficiency: Friction, design of machine, lubrication, and material quality.
  • Ideal Machine: Would have 100% efficiency (M.A. = V.R.), but impossible in practice.

Levers

  • Lever: A rigid rod that can rotate about a fixed point called fulcrum.
  • Three Classes of Levers: Based on positions of fulcrum (F), effort (E), and load (L).
  • Class I: Fulcrum between effort and load (F-E-L). Examples: seesaw, crowbar, scissors.
  • Class II: Load between fulcrum and effort (F-L-E). Examples: wheelbarrow, nutcracker, bottle opener.
  • Class III: Effort between fulcrum and load (F-E-L). Examples: tweezers, fishing rod, human forearm.

Pulleys

  • Pulley: A grooved wheel that rotates about an axle, with a rope running over it.
  • Single Fixed Pulley: M.A. = 1, V.R. = 1. Used only to change direction of force.
  • Single Movable Pulley: M.A. ≈ 2, V.R. = 2. Provides mechanical advantage.
  • Block and Tackle System: Combination of fixed and movable pulleys. V.R. = number of supporting strings.
  • Applications: Cranes, elevators, flag poles, and wells.

Formulas

Keep these ready

Formula 01

Mechanical Advantage (M.A.) = Load / Effort

Ratio of output force to input force

Formula 02

Velocity Ratio (V.R.) = Distance moved by Effort / Distance moved by Load

Ratio of distances or velocities

Formula 03

Efficiency (η) = (M.A. / V.R.) × 100%

Percentage efficiency of a machine

Formula 04

Efficiency (η) = (Work Output / Work Input) × 100%

Alternative formula for efficiency

Quiz

Test your knowledge

Multiple choice

  1. Question 1 of 10Knowledge
    The mechanical advantage of a machine is defined as:
  2. Question 2 of 10Knowledge
    The velocity ratio of a machine depends on:
  3. Question 3 of 10Knowledge
    The efficiency of a real machine is always:
  4. Question 4 of 10Knowledge
    A single fixed pulley has a mechanical advantage of:
  5. Question 5 of 10Knowledge
    In which class of lever is the fulcrum between the effort and the load?
  6. Question 6 of 10Knowledge
    A wheelbarrow is an example of:
  7. Question 7 of 10Comprehension
    For an ideal machine:
  8. Question 8 of 10Comprehension
    If the efficiency of a machine increases, which of the following must be true?
  9. Question 9 of 10Assertion-Reasoning
    Assertion (A): A machine with M.A. less than 1 is useless. Reason (R): Such machines are used as speed multipliers.
  10. Question 10 of 10Knowledge
    The V.R. of a block and tackle system is equal to:

Practice numericals

  1. Problem 1 of 5Application
  2. Problem 2 of 5Application
  3. Problem 3 of 5Application
  4. Problem 4 of 5Application
  5. Problem 5 of 5Application

0 of 15 answered