Answer:
Part(a) The work done by gravitational force on the book as it is dropped to her hands is <em><u>167 Joules</u></em>
Part(b) The change in the gravitational potential energy() of book earth system is <em><u>-167 Joule</u></em>
Explanation:
Part (a)
Since the work done (W)= Force(F)x Displacement(D) in the direction of force
Here force is applied by gravity in downward direction (towards the center of the earth),
And displacement in the direction of force is D= (10-1.5) m = 8.5 m
Therefore work done ,
where mass, m =2 kg and acceleration due to earth's gravity ,
=>
Thus the work done by gravitational force on the book as it is dropped to her hands is <em><u>167 Joules</u></em>
Part (b)
By the work energy theorem , Change in the gravitational potential energy ()= - Work done by gravitational force ()
=>
Thus the change in the gravitational potential energy() of book earth system is <em><u>-167 Joule</u></em>