How does a lever increase the distance but decrease the force? And how does it help us in real life?

Answer 1

Your question is somewhat the opposite of what the actual application of levers is generally used for.

Levers work simply be trading distance for increased force. A car jack is a good example - with minimum force over a greater distance, you can easily lift a 3000 pound vehicle.

A pair of scissors works just the other way around - a shorter movement of the handles results in a greater, but less forceful, movement of the blades.

The ratio is proportional - if a lever is 2" from the fulcrum and the handle is 10" long, the mechanical advantage will be 5:1 (i.e. 10/2).

In real life, levers are used constantly, from a pair of pliers to a diesel powered back hoe.

Answer 2

it is because of something we call torque. Torque is the cross product of force (F) and the distance from the axis of rotation (r). Thus when you have an object on a lever, its torque is its wieght which is a force times its distance from the fulcrum. F*r on the other side if you have a longer distance r, to keep the equation equal you must have a smaller force. For example you have a 10N box on a lever that is 3 meters from the fulcrum. that is 30 M*m of torque. On your side the distance from the fulcrum is 5 meters. To raise the box, you would only need to apply 6N of force 6*5=3*10