Question

If a body of mass 20gm falls from a height 200m
and its total P.E. is converted into K.E., at the point
of contact of the body with earth surface, then
what is the decrease in P.E. of the body. (g = 10
m/s
(1) 20 J
(2) 40 J
(3) 60 J
(4) 90 J​

Answer 1

Answer:

Option number (2) 40 Joule is the correct answer.

Decrease in PE is 40 Joule.

Explanation:

Given,

Mass of body = 20 gm = 20/1000 kg

Mass of body = 0.02 kg

Height of body = 200 m

(PE) i = mgh

(PE) i = 0.02 × 20 × 200 joule

(PE) i = 40 Joule

In case of contact of the body with earth surface.

Given,

Total P.E. is converted into K.E

Then,

(PE) f = 0 Joule

Here,

PE is the potential energy.

m is the mass of body.

g is the acceleration due to gravity.

h is the height of body.

(PE) i is the intial potential energy of the body.

(PE) f is the final potential energy of the body.

According to the question

Decrease in PE = (PE) i - (PE) f

Decrease in PE = (40 - 0) Joule

Decrease in PE = 40 Joule.

Hence,

Decrease in PE is 40 Joule.