1
AIPMT 2014
+4
-1
A black hole is an object whose gravitational field is so strong that even light cannot escape from it. To what approximate radius would earth (mass = 5.98 $$\times$$ 1024 kg) have to be compressed to be a black hole?
A
10$$-$$9 m
B
10$$-$$6 m
C
10$$-$$2 m
D
100 m
2
NEET 2013 (Karnataka)
+4
-1
A particle of mass 'm' is kept at rest at a height 3R from the surface of earth, where 'R' is radius of earth and 'M' is mass of earth. The minimum speed with which it should be projected , so that it does not return back, is
(g is acceleration due to gravity on the surface of earth)
A
$${\left( {{{GM} \over {2R}}} \right)^{1/2}}$$
B
$${\left( {{{gR} \over 4}} \right)^{1/2}}$$
C
$${\left( {{{2g} \over R}} \right)^{1/2}}$$
D
$${\left( {{{GM} \over R}} \right)^{1/2}}$$
3
NEET 2013 (Karnataka)
+4
-1
The radius of a planet is twice the radius of earth. Both have almost equal average mass densities. VP and VE are escape velocities of the planet and the earth, respectively, then
A
VP = 1.5 VE
B
VP = 2 VE
C
VE = 3 VP
D
VE = 1.5 VP
4
NEET 2013
+4
-1
A body of mass 'm' is taken from the earth's surface to the height equal to twice the radius (R) of the earth. The change in potential energy of body will be
A
3mgR
B
$${1 \over 3}$$mgR
C
mg2R
D
$${2 \over 3}$$ mgR
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