Question

In which of the following cases is a work done positive zero or negative? (i)work done by a porter on suitcase in lifting it from the platform on to his head.. (ii)work done by the force of gravity on a suitcase as the suitcase falls down from the porter's head.. (iii)work done by a person on a book held in his hand while walking with uniform speed on a horizontal road.

Answer 1

1 st will be +ve
2nd will be -ve
3rd will be 0