Gravitation

Question : 18

Total: 25

The escape speed of a projectile on the earth’s surface is 11.2 km‌s–1. A body is projected out with thrice this speed. What is the speed of the body far away from the earth? Ignore the presence of the sun and other planets.

Solution:

Using law of conservation of energy

mv02=

mv2−

mvE2
⇒v0=√v2−vE2
=√(3vE)2−vE2=√8vE [Given‌v=3vE]
=√8×11.2=31.68‌km‌s−1
Here, v0= speed of projectile when far away from the earth
v= velocity of projection of the body, vE= escape velocity

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