A tower crane and its counterweight
Two cranes hold the same load. One has a counterweight and its jib stays level; the other’s jib tips over.
2D
Age 8+10 min
Levers & balanceStability
Loading simulation…
Press “Run”. Bodies move by the laws of physics: gravity, friction, elasticity.
What the experiment shows
A crane jib is a lever pivoting on the tower. A heavy counterweight on the short arm balances the load on the long arm.
How to run it
- Press “Run” and compare the two cranes.
- Move the load closer to the tower on the crane without counterweight.
- Find the counterweight mass that keeps the jib steadiest.
Questions to discuss
- Why can’t a crane lift a heavy load at the very tip of the jib?
- Where is the lever rule in a crane?
The science
The lever rule: m₁·l₁ = m₂·l₂. A 4 kg counterweight 1 m from the tower balances a 1 kg load 4 m away. If the moments differ, the jib turns.
Try it at home
Lay a ruler on a pencil, put an eraser on one end and find where to place coins to balance it.
What to change in the editor
- Make the counterweight twice the load.
- Lengthen the load cable.