Asteroid Ida Was Photographed by the Galileo Spacecraft in 1993 $4.5 \times 10 ^ { 16 } \mathrm {~kg}$

Multiple Choice

Asteroid Ida was photographed by the Galileo spacecraft in 1993 , and the photograph revealed that the asteroid has a small moon, which has been named Dactyl. From the dimensions of Ida and its general features, one can estimate the mass of Ida to be $4.5 \times 10 ^ { 16 } \mathrm {~kg}$ , and the distance between Dactyl and Ida is approximately 90 \mathrm{~km} . Assuming a circular orbit, what would be the orbital speed of Dactyl? $\left( G = 6.67 \times 10 ^ { - 11 } \mathrm {~N} \cdot \mathrm { m } ^ { 2 } / \mathrm { kg } ^ { 2 } \right)$

A) 2.9 m/s
B) 30 m/s
C) 2.3 m/s
D) 5.8 m/s
E) 11 m/s