7.6.1 Pulley

Last updated at September 16, 2026 by

What is a Pulley?
  • A pulley is a wheel with a groove that guides a rope .
  • The rope sits in the groove and moves over the wheel.
    Example: You may have seen a flag or a load being raised — the rope is pulled in the downward direction, while the flag or the load moves in the upward direction. This is done with the help of a pulley fixed at the top.
  • GIF Watch: what is a Pulley Animation for "What is a Pulley". A short looping GIF, three or four beats, drawn in the flat classroom style of the chapter. Beat 1 — A pulley is a wheel with a groove that guides a rope. Beat 2 — The rope sits in the groove and moves over the wheel. Label every arrow and quantity, name the direction each force or motion acts in, and hold the last frame for a moment before the loop starts again.
How does a fixed pulley help us?
  • A fixed pulley does not reduce the magnitude of the force required.
  • It only changes its direction .
  • It is easier for us to pull downward than to lift a load by applying an upward force directly.
  • Thus, the pulley provides convenience by changing the direction of the effort.
What is the Mechanical Advantage of a fixed pulley?
  • In a fixed pulley, the effort and the load are equal in magnitude.
  • Mechanical advantage = Load / Effort
  • Load = Effort, so
  • Mechanical advantage of a fixed pulley = 1
    Example: Bucket of weight 50 N, we pull the rope with 50 N.
    MA = 50 / 50 = 1
Can a pulley have Mechanical Advantage more than 1?
  • Yes — using movable pulleys or a system of pulleys .
  • GIF Watch: can a pulley have Mechanical Advantage more than 1 Animation for "Can a pulley have Mechanical Advantage more than 1". A short looping GIF, three or four beats, drawn in the flat classroom style of the chapter. Beat 1 — Yes — using movable pulleys or a system of pulleys. Beat 2 — In a movable pulley system. Beat 3 — Such systems can have mechanical advantage greater than 1 — they can lift much heavier objects with much smaller effort. Label every arrow and quantity, name the direction each force or motion acts in, and hold the last frame for a moment before the loop starts again.
  • In a movable pulley system
    • The load is attached to the movable pulley.
    • One end of the rope is fixed to a point.
    • The other end is free to apply effort.
  • Such systems can have mechanical advantage greater than 1 — they can lift much heavier objects with much smaller effort.
  • Pulleys are widely used in real life, such as in elevators and cranes , given the convenience they provide us.
  • 📋 Revise, Reflect, Refine, Q7 (Page 137)
    Which factors determine the energy required to raise a flag from the ground to the top of a tall flagpole using a pulley? Does raising the flag slowly or quickly change the amount of work done? If the speed at which the flag is raised is doubled, how does the power requirement change? Explain your answers.
    View answer Hide answer
    Answer
    • Which factors determine the energy required?
      • Energy required = work done = mgh
      • So it depends on — the mass of the flag (m) and the height of the flagpole (h).
    • Does raising the flag slowly or quickly change the work done?
      • No. Work = mgh — it has no time in it.
      • Slow or fast, the work done is the same .
    • If the speed of raising is doubled, how does the power change?
      • Doubling the speed means the same work is done in half the time .
      • Power = Work / time = W / (t/2) = 2 × (W/t)
      • So the power requirement doubles .
📝 Important points — 7.6.1 Pulley
Point Detail
Pulley Wheel with a groove that guides a rope
Fixed pulley Changes only the direction of force
MA of fixed pulley 1 (effort = load)
Movable pulley system MA > 1 — lifts heavier loads with smaller effort
Real life use Wells, flagpoles, elevators, cranes
💡 Worth remembering
  • Fixed pulley = direction changer, not force reducer.
  • Pull DOWN to lift UP — that is the whole convenience.
  • For force multiplication, the pulley must be movable.
✅ Quick self-check
  1. A flag of weight 20 N is raised using a fixed pulley. How much effort is needed?
    View Answer Hide Answer
    • For a fixed pulley, Effort = Load.
    • Effort = 20 N
  2. What is the mechanical advantage of a fixed pulley?
    View Answer Hide Answer
    • Effort = Load in a fixed pulley.
    • MA = Load / Effort
    • MA = 1
  3. If a fixed pulley does not reduce the force, why do we still use it?
    View Answer Hide Answer
    • It changes the direction of the effort.
    • Pulling down is more convenient than lifting up.

Key terms and units

Term Meaning
Pulley Wheel with a groove guiding a rope
Fixed pulley Pulley fixed at a point, MA = 1
Movable pulley Load attached to the pulley, MA > 1
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