The figure shown below illustrates a lever being used to lift a weight W.
The applied force is F.
In order to lift the weight, the minimum applied force is
F*b = W*a
F = (a/b)W
When the ratio a/b < 1, then the applied force is less than the weight.
The principle behind the use of a lever is to keep the ratio a/b small in order to decrease the effort force.
Answer: A
A lever is used to decrease effort force.
