Question

Define work. Give SI unit of work done. Write an expression for Positive for positive work done.

Answer 1

When a force acts upon an object to cause a displacement of the object, it is said that work was done upon the object
The SI unit of work is Joules 
W= FS cos Ф

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Answer 2

work is said to be done whenever a force acts on a body and the body moves due to the force.The S.I unit of work is Joule.one joule of work is said to be done when a force of one newton displaces a body through a distance of 1 meter in its own direction.work done =Fs