Question

Define 1J of work.

Answer 1

Hint: 1J is the S.I. unit of work. So, firstly define the basic definition of what work is and describe it in terms of units of the basic physical quantities used in order to obtain 1 Joule. The basic units of 1 joule is equivalent to $ {kg{m}^{2}}/{{s}^{2}}$.

Complete solution:
Joule which is denoted by J is a unit of work. This S.I. the unit is kept in honor of James Prescott Joule. A British physicist. Work can be defined as the measure of displacement of an object or a point. It can also be said that the work is a mechanical manifestation of energy.
In the international Systems of Units i.e. S.I., 1 Joule of work is defined as the energy transferred to an object when a force of one Newton denoted by N, acts on that object in the direction of its motion through a distance of one meter. So, mathematically we can write it as,
$1J= Nm$
We can, work is given by,
$W= F.s$ …(1)
Where,
$W$ is the work done
$F$ is the force applied
$s$ is the displacement
We also know, S.I. the base unit of force is $ {kg.m}/{{s}^{2}}$ and that of displacement is m. Also, the S.I. the unit of Work is J.
So, substituting these units in the equation. (1) we get,
$J= {kg.m}/{{s}^{2}} \times m$
$\Rightarrow J= {kg{m}^{2}}/{{s}^{2}}$

Note:
Newton meter is a unit of torque also which can make students confused. There are some other commonly used units for work such as erg in the CGS system, horsepower-hour, foot-pound, kilowatt-hour etc. Students must remember that work has similar physical dimensions as heat, thus measurement units such as BTU, calorie, Calorie are also used for measuring work done.