Question

What is the work done to lift an object weighing 100 g to a height of 50 m from an initial height of 20 m? (Assume g =10 $m{s}^{-2}$)

• A. 20 J
• B. 30 J
• C. 50 J
• D. 70 J

Answer 1

The correct option is B

30 J

Here, work done to lift an object is the work done against the gravitational force.

Force required to lift the object is equal to the product of mass and acceleration due to gravity (g =10 $m{s}^{-2}$).

Here, mass of the object, m = 100 g = 0.1 kg

Intial height = 20 m

Final height = 50 m

So, force = $m\times g$ = $0.1\times 10$ = 1 N

Work done = Force $\times$ Displacement

= 1 $\times$ (50-20)

= 30 J

$\therefore$ Work done to lift the object is 30 J.