Question

a body of mass 20kg is rest on the earths (1)find its gravitational potential energy (2)Find the kinetic energy to be provided to the body to make it free from the gravitational influence of the earth

Answer 1

Answer:

Data : m = 20 kg , g = 9.8 m/s2,R=6400km=6.4×106m/s2,R=6400km=6.4×106m

(i) The gravitational potential of the body

−GMmR=−mgR(∴g=GMR2)-GMmR=-mgR(∴g=GMR2)

=−20kg×9.8m/s2×6.4×106m=−1.2544×109J=-20kg×9.8m/s2×6.4×106m=-1.2544×109J

(ii) To make the body free from the gravitational influence of the earth , it should be provided kinetic energy equal to 1.2544×1091.2544×109 J

Answer 2

Answer:

Solution :

Data: m = 20 kg, g = 9.8 m /s?, R = 6400km

6.4 x 10°m <br> The gravitational potential of the body <br>

GMm GM

R?

R

mgR

<br>

20kg x 9.8m / s2 x 6.4 x 106m = <br>

(ii) To make the body free from the gravitational influence of the earth, it should be provided kinetic energy equal to

1.2544 x 10^9