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Physics

During his experiments with a single movable pulley, Jas determined the effort, mechanical advantage and efficiency as X, Y & Z, respectively. Subsequently, after lubricating the pulley thoroughly, he recalculated the effort, MA and efficiency. X', Y' & Z' respectively. Which of the following relationships accurately represents the scenario?

  1. X' > X
  2. Y' < Y
  3. Z' > Z
  4. Z' = Z

Machines

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Answer

Z' > Z

Reason — Lubrication reduces friction at the axle of the pulley. This has three main effects:

  1. Less effort (X') is needed to lift the same load (X' < X).
  2. Since the machine now wastes less energy, the efficiency (Z') increases (Z' > Z).
  3. Mechanical Advantage (Y'), which is Load/Effort, increases because the effort decreases while the load stays the same.
  • Option (1): X’ > X Incorrect (It actually decreases)
  • Option (2): Y’ < Y Incorrect (MA increases)
  • Option (3): Z’ > Z Correct
  • Option (4): Z’ = Z Incorrect (Efficiency increases)

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