The SI unit of work

1. Work
Meaning and SI unit of Measurement

2. The contents
• The meaning of work
• The relationship between force and work
• The unit of force
• The unit of distance
• The unit of work
• The SI unit of work

3. The meaning of work
• Work is done if force is applied and the force causes movement.
• The movement should be in the direction of the force.
• If force is applied and no movement results, no work is done.
• Movement cannot occur if there is no force applied
• This means force can be defined as the product of force and
distance.

4. The relationship between force and work
• Force and work are inseparable.
• This has been seen in the meaning of work.
• Work cannot be done without the application of force.
• Force can be applied yet no work is done if the force does not
cause movement.
• Movement cannot occur if force is not applied.
• This means that force is the anchor of work – no force, no work.

5. The unit of force
• Recall that force is a derived quantity.
• It is derived from mass and gravity.
• A gravitational field constant of about 10N is exerted per Kg of
matter on earth.
• Hence to find force we multiply mass and the gravitational field
constant on earth.
• This means the unit of force is the Newton upon cancellation of
the Kg’s (thus Kg × N/Kg = N).

6. The unit of distance
• As you may recall, distance is a fundamental (basic) quantity.
• Thus distance is not expressed in terms of any other quantities.
• The unit for measuring distance is the metre (m) and this unit is
not derived from any other unit.

7. The unit of work
• Recall that we have defined work as the product of force and
distance.
• The word product means multiplication.
• This means to calculate work you multiply force and distance.
• The units of force and distance will give you the unit for work.
• This unit is the Newton metre (Nm).

8. The SI unit for work
• Recall that an SI unit is an internationally recognized unit.
• The Newton metre is not the SI unit of work.
• The SI unit of work is the Joule (J)
• 1J is equal to 1Nm.
• This means 1 Joule is the work done to move 1Kg of a substance
through 1m.

9. END OF PRESENTATION
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