Home » Ask & Discuss » Physics. » Mechanics « Back to Discussion

Mechanics

Blazing goIITian

Joined:	6 Mar 2010
Post:	380

17 Mar 2010 19:43:50 IST

0 People liked this

235

The K.E needed to project a body of mass m from the earth's surface to infinity is {explain}......

Physics , Mechanics , Kinematics , Newtons laws CircularMotion , Work Power Energy collisions , Rotation , Gravitation , Simple Harmonic Motion , Fluid Mechanics , Materials Wave Sound , Super Position , units dimensions , com momentum , shm , wave sound

The K.E needed to project a body of mass m from the earth's surface to infinity is {explain}...........a) mgR b) 2mgR c)1/2 mgR

Share this article on:

Comments (4)

shashank agarwal

Blazing goIITian

Joined: 25 Jul 2009

Posts: 601

17 Mar 2010 21:46:25 IST

Like 0 people liked this

(a) is correct

mardav, NIT-B civil engineering.

Blazing goIITian

Joined: 9 Feb 2009

Posts: 619

17 Mar 2010 21:46:54 IST

Like 0 people liked this

yes.a) is correct

Aakash Anuj

Blazing goIITian

Joined: 26 Mar 2009

Posts: 1428

18 Mar 2010 17:49:05 IST

Like 0 people liked this

when the body is at infinity,, the sum of the KE and PE is zero. hence the total initial energy should also bezero. Conserving ergy, GMm/R = 1/2mv^2 we get v=root (2gR) which is independent of the mass of the body. hence option A is correct.

edison

Forum Expert

Joined: 19 Oct 2006

Posts: 7452

18 Mar 2010 17:55:23 IST

Like 1 people liked this

The KE needed to project the body of mass 'm' from the earth's surface to infinity is equal to the Graviational Potential Energy (PE) of mass and earth system,

i.e. KE = PE

or KE = GM_em / R

But GM/ R² = g

or GM/R = gR

Thus KE = mgR

Hence correct option is (A)

Quick Reply

Reply

	Some HTML allowed.
	Keep your comments above the belt or risk having them deleted.
	Signup for a avatar to have your pictures show up by your comment
	If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team