Question

A stone of mass 500 gram is thrown vertically upward with a velocity of 15 m/s.
Calculate
(i) the potential energy at the greatest height .
(ii) the kinetic energy on reaching the ground and
(iii) the total energy at it’s halfway.

Answer 1

Answer:

Kinetic Energy, K.E=0.5×m×v

2

K.E=0.5×0.5×15×15=56.25J

As it has 56.25 J at the initial point as total energy, at some point X,Potential Energy(P.E.) is maximum.

Total energy=P.E.+K.E.

56.25=P.E.+K.E.

As energy is conserved total energy at point X also must be 40 J.

For P.E to be maximum K.E. must be zero.

Hence P.E.=56.25J

We can come to the conclusion that potential energy will have the maximum value at maximum height.

Answer 2

using

v^2 - u^2 =2as  we have

0 - 225 = 2(-9.8) s

s = 225 /20 = 125 /9.8 = 11.5 m

1) potential energy at highest point = mgh = .5 (9.8) (11.5) = 56.35J

2) on reaching ground all the potenial energy will change into kinetic energy

so kinetic energy on groung = 56.35J

3) total energy remains same and is 56.35J