Question

A boy moved a body through $3m$ in four different ways. In which of the following cases was the work done the maximum.
A) Pushing a body over an inclined planes
B) Lifting a body vertically upward
C) Pushes a body over smooth rollers
D) Pushing on a plane of horizontal surface

Answer 1

Hint : Work is the product of force and displacement and SI units of work are joules. The dimensional formula of work is $M{{L}^{2}}{{T}^{-2}}$ and force is vector quantity and its unit is newton. Work is a scalar quantity and the factor which affects the work is force and displacement is a vector quantity which has both direction and magnitude.

Complete step-by-step solution:
Work is defined as the amount of energy transformed by a force and a stored work is called energy. Work is not related to time and work can be done very quickly or else very slowly. There are three types of work and those are positive, negative and zero work. In zero work the force and displacement are perpendicular to each other.
Work is the product of force and displacement.
Mathematically the work done is expressed as :
$W=F\times S\cos \theta$
$\theta$ = Displacement angle
The displacement angle is ${{180}^{0}}$ when the body is lifted vertically upwards
Therefore $\cos {{180}^{0}}=1$
Hence the work done will be maximum when the displacement angle is equal to ${{180}^{0}}$ anything but vertically upwards.
So the correct option is B.

Note: Students work and energy are directly proportional to each other and energy can be converted into different forms. Energy which cannot be created is distorted but it can be transformed .SI unit of energy is also joules so don’t confuse work and energy. Energy is a scalar quantity which has only magnitude.