Physics

Problem

An asteroid moves around the Sun in an almost circular orbit whose semi-major axis is

4.0\,\text{AU}

. Assume

1\,\text{AU}=1.5\times10^{8}\,\text{km}

and Earth’s orbital period is

1.0\,\text{year}=3.156\times10^{7}\,\text{s}

. The asteroid’s average orbital speed is closest to a)

20\,\text{km\,s}^{-1}

15\,\text{km\,s}^{-1}

10\,\text{km\,s}^{-1}

7.5\,\text{km\,s}^{-1}