Question

a boy has to apply an upward force of 4N on a book to lift it from the ground to a desk. if he does 3J of work what is height of desk?

Answer 1

work done = applied force × displacement .

here displacement means height of desk .

now,
3j = 4N × height of desk

height of desk = 3/4 m = 75 cm

Answer 2

Force = 4 N
Work = 3 J

s = displacement = height

Work done = Force x s
3 = 4 x s
s = 3 / 4
s = 0.75 m

height of desk = 0.75 m