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Lift a brass weight with one wheel, then with more. How hard do you have to pull?
Pulleys and a Newton Meter lab · Last updated: 16 October 2026
You lift a brass weight using a rope over a single pulley, then add more wheels and lift it again, reading the pull on a newton meter each time. The weight never changes, yet the pull does. Why?
What you'll discover
- A single fixed pulley changes the direction of your pull but not its size.
- Adding moving pulleys shares the weight between several lengths of rope, so you pull less hard.
- The catch is that you must pull more rope through to lift the weight the same height.
The science in plain words
A pulley is a wheel with a groove that a rope runs over. With one fixed pulley at the top, you pull down to lift the weight up. That is handy, because pulling down lets you use your own body weight, but the force you need is the same as the weight of the load.
Things change when a pulley is attached to the load and moves up with it. Now the load hangs from two lengths of rope, and each carries half of it. So you need only about half the force. With more pulleys, the load is shared between even more strands, and the pull drops further.
Physics never gives something for nothing, though. If two strands hold the load, you must pull two metres of rope to raise it one metre. Force times distance, which scientists call work, stays about the same. Pulleys trade a smaller force for a longer pull.
In real pulleys friction in the wheels and the weight of the moving pulleys add a little extra. Cranes, flagpoles, lifts and sailing boats all use pulley systems to lift heavy loads with less effort.
Where it fits
- India, NCERT: Pulleys are not a separate topic in the current NCERT classes 6 to 10 books; the idea of work as force times distance appears in Class 9 Chapter 10: Work and Energy.
- United States: Grades 6 to 8
Common questions
How does a pulley make lifting easier?
A single fixed pulley lets you pull down instead of up. With moving pulleys, the load is shared by several lengths of rope, so you need less force, though you have to pull more rope.
What is mechanical advantage?
It is how many times a machine multiplies your force. A pulley system where four strands hold the load has a mechanical advantage of about four, so you pull with roughly a quarter of the weight.
Do pulleys save energy?
No. They reduce the force needed, but you pull the rope a longer distance, so the work you do is the same or slightly more because of friction.
Related labs
- Gear Mechanisms: Big gear, small gear: which one turns faster, and why?
- Hydraulics: Push a little piston gently. Can the oil lift a heavy crate?
- Ruler See-saw: Hang brass weights on a ruler. Can a light weight far out balance a heavy one close in?
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Try it yourself
The Pulleys and a Newton Meter lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.