A spaceship goes into a circular orbit close to the earth's surface. What additional velocity must be imparted to the ship so that it is able to escape the gravitational pull of the earth? (R=6400km, g=9.8 m s−2)
A
7km s−1.
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B
3.278km s−1.
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C
5km s−1.
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D
9km s−1.
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Solution
The correct option is B3.278km s−1. The orbital velocity in a circular orbit close to the earth is v=√gR. The velocity required to escape ve=√2gR. Hence additional velocity required is ve−v=(√2−1)√gR. Therefore, ve−v=0.414×√9.8×6400×103 =3278.71m/s =3.278km s−1.