The planet Mars has a mass of 6.417×1023 kg. The small moon Phobos orbits Mars in a near circular orbit at an orbital distance (from the centre of Mars to the centre of Phobos) of 9,376km. Phobos has a mass of 1.066×1016 kg and a mean radius of 11.27 km. As an approximation you may assume the moon is spherical. It is in a tidally locked orbit so that the same side of Phobos faces Mars all the time.

Calculate the angular velocity w of Phobos.
Suppose there is some loose material on the surface of Phobos facing Mars. Write an
expression for the total gravitational force acting on the material.