What is the mechanical advantage of the frictionless plane shown below?

Inclined plane

A. 0.64

B. 1.31

C. 1.4

D. 1.56

D: 1.56

Explanation:

On a frictionless plane, W||=Wsin(θ). To push the brick up the plane, the car has to push with a force just greater than W||. To lift the brick directly, a force just greater than W must be used. The mechanical advantage is the ratio of the force needed to lift the brick directly to the force needed to lift the brick with the plane:

MA=Force needed to lift object without inclined plane/Force needed to lift object with inclined plane

MA=W/W||

MA=W/Wsin(θ)

MA=1/sin(40∘)

MA=1.56