Question 4: Explain how cranes are able to lift heavy loads without toppling?

Answer

The mystery rests in the design of the crane.
Body and particularly the base of the crane is made very heavy. Its height from the ground is quite less. This excessive weight and closeness to the ground makes a crane more stable.
On the other hand, the arm which lifts the load is made longer. We know that torque is proportional to the moment arm. The lengthy moment arm enables the machine to exert less force to lift the load.
Both these factors help the crane to lift heavy weight without toppling itself.