(1) Assume the radius of the earth is 6400 km and gravity at a height of 200 km

Question

(1) Assume the radius of the earth is 6400 km and gravity at a height of 200 km is 9.2 m/s2. A satellite orbits the earth 200 km above the surface. The speed necessary for a circular orbit is most nearly

(A) 6000 m/s (b) 6600 m/s (c) 7200 (d)7800

(2) What must be true for the center of gravity of an object to coincide with the object’s center of mass?

( I )..The gravitational field must be constant over the volume of the object.

( II )..The object must be symmetrical about three axes.

( III )..The object must have constant density

(A) I only .......(B) I and II .... (C) II and III .... . (D) I, II and III

Explanation / Answer

(1) centripetal acc. a_c = 9.2 m/s^2

a_c = v^2 / r

9.2 = v^2 / (6400 x 10^3 + 200 x 10^3)

v = 7792 m/s

Ans(d)

(2) Ans(C)

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