Give one situation in which one of the forces acting on the object is doing positive work and the other is doing negative work. Calculate the work done in lifting a box weighing 150 kg through a vertical height of 7 meteres. (g = 10 m/s2)

Asked by Sthitaprajna Mishra | 17th Feb, 2014, 08:50: PM

Expert Answer:

Example:

Work done in pulling a bucket of water from the well is positive as the displacement and applied force to pull the bucket are in the same direction.  

At the same time work done by gravitational force on a bucket of water is negative because bucket is being pulled upward and gravitational force is acting downward. Hence the direction of force and displacement is opposite to each other.

W = mgh

    = 150 x 10 x 7

    = 10500 J

Answered by  | 18th Feb, 2014, 12:03: PM

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