Unit of Work

Work is defined as the measure of the displacement of an object or a point. Some common examples of force include riding a bike uphill or carrying something in the presence of the earth’s gravity. In essence, work is nothing but a mechanical manifestation of energy. It is represented as W.

Mathematically, it is represented as follows;

 $$\begin{array}{l}W=Fd\;cos\theta\end{array}$$

Where,

• F is the force applied
• d is the displacement

Let’s look at the work units below.

SI Unit of Work

The SI unit of work is joule (J). Joule is defined as the work done by a force of one newton causing a displacement of one meter. Sometimes, newton-metre (N-m) is also used for measuring work. However, as this unit is also used for torque it can get quite confusing. Thus, SI authority does not encourage anyone to use this unit.

Following is the table of units and dimensional formula:

 SI unit N.m Joule CGS unit dyne-cm Erg Dimensional formula ML2T-2 –

Watch the video to find out what are base measurements

Other Units of Work

Some commonly used work units also include erg in the CGS system, the horsepower-hour, the newton-metre, the foot-pound, the kilowatt-hour, the foot-poundal, and the litre-atmosphere. Notably, work has a similar physical dimension as heat; therefore, measurement units such as BTU, therm and Calorie, are also used for measuring work done.

Converting The Units Of Work

 Units Equivalent Unit in Joules 1 erg 1.0E-7 J 1 horsepower-hour 2684519.54 J 1 newton-metre 1 J 1 foot-pound 1.35582 J 1 kilowatt-hour 3.6e+6J 1 BTU 1055.06 J

The below video helps to revise the concepts in the chapter Work and Energy Class 9

Q1

Define work.

Work is the measure of the displacement of an object or a point.
Q2

What is the formula to represent work?

$$\begin{array}{l}W=Fd\;cos\theta\end{array}$$
Where,
• F is the force applied
• d is the displacement
• Q3

What is the SI unit of work?

The SI unit of work is joule (J).
Q4

What is a joule?

Joule is defined as the work done by a force of one newton causing a displacement of one meter.
Q5

List three units of work in CGS system.

• Horsepower-hour
• Newton-metre
• foot-poundal
• Watch the video and solve NCERT exercise questions in the chapter Work and Energy Class 9

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