Has an object in motion ability to do work ?

The ability to do work is called

Which of the following does not possess the ability to do work not because of motion ?

(a) Can distance travelled by an object in motion be negative? (b) Can displacement of an object in motion be zero or negative ?

Fill In the blanks: __ is the ability to do work and is expressed in units of __

Three friends Priya, Usha and Spandana together can do a piece of work in 56 days. If Usha's ability to do the work is twice as that of Spandana and Priya's ability to do the work is twice as that of Usha, then find the number of days required for these friends to complete the same work if they work individually.