Grades 3–5 · Machines
How does a counterweight help an elevator move?
A traction elevator connects its car to a counterweight with ropes or belts passing over a driven wheel. When the car rises, the counterweight descends. When the car descends, the counterweight rises. Their opposite movement is part of one connected mechanism.
In the diagramA traction elevator has an opposing massCarCounterweight600 + 200 kg800 kgConnected masses move in opposite directionsThe selected masses balance
The counterweight balances some of the car's weight, including part of its possible load. In the illustration, the empty car has a mass of 600 kilograms and the counterweight 800 kilograms. Adding a 200-kilogram load makes the car side 800 kilograms too, so the selected masses balance.
A lighter load makes the counterweight side heavier; a larger load can make the car side heavier. The drive manages that difference rather than lifting an unbalanced car alone. Balanced masses do not mean a real elevator needs no energy or control. Starting, stopping and overcoming rubbing still matter, and the drive must control movement in either direction.
About this explanation
Starting knowledge: Add mass amounts and recognize that connected objects can move in opposite directions.
Sources
- Otis — Understanding the Basic Workings of a Lift