Question

When a person lifts a brick above the surface of the earth, then its potential energy
(a) increases (b) decreases
(c) remains same (d) None of these

Answer 1

Explanation:

a) increases

ENERGY CAN NEVER BE CREATED NOR BE DESTROYED.

When we lift any object above the ground, it gains potential energy as it is now at a particular height with respect to the ground (which is the datum here).

POTENTIAL ENERGY = mgh

where m= mass of the object , h=height to which the object is raised , g=acceleration due to gravity

Now one may ask that from where this energy came?

This energy is supplied by the person himself lifting the object as he is doing an amount of muscular work in lifting it which is converted into the potential energy of the body.

Hope this helped!

Answer 2

Explanation:

• When an object is being lifted, the conservative force within the system (gravity, in this case) does negative work. This adds to the energy of the system. Hence an increase in the potential energy.
•  Gravitational potential energy of body of mass m at a height of h above the surface of earth (M = mass of earth , R = radius of earth)

•   Gravitational potential energy of a body of mass m at a height h above the surface of earth is given by -GMmR + h.

•    "ENERGY CAN NEVER BE CREATED NOR BE DESTROYED."

So , the potential energy increases.

ANSWER: Option A