Question

21. The escape velocity from earth is 11 km/
sec. The escape velocity from a planet having
nine times the radius and one third of
density as earth is __ Km/sec
1) 11 2) 22/33) 33 13 4) 44/3​

Answer 1

Answer:

C

22kms

−1

Given : v

e

=11 km/s R

p

=2R

e

ρ

p

=ρ

e

Escape velocity v=

R

2GM

=

R

2G×

3

4

πR

3

ρ

=

3

8

πGR

2

ρ

⟹ v∝

ρR

2

∴

v

e

v

p

=

ρ

e

R

e

2

ρ

p

R

p

2

Thus we get,

11

v

p

=

ρ

e

R

e

2

ρ

e

(2R

e

)

2

=2

⟹ v

p

=22 km/s