Answer:
a) 29.4 J
b) - 29.4 J
Explanation:
Given:
Mass of the book, m = 2 kg
Height above the floor, h = 1.5 m
Now,
the work done by the person will be = Force applied on the book × displacement of the book
thus,
Work done by the person = mg × h
where, g is the acceleration due to gravity
thus, on substituting the values, we get
Work done by the person = 2 × 9.8 × 1.5 = 29.4 J
now,
for the force applied by the gravitational pull (downwards) the displacement is in opposite direction (upwards) to the force of the gravity.
Thus,
work done by the gravity will be negative
therefore, the work done by the gravity = - mg × h
or
work done by the gravity = - 29.4 J
