physics
posted by sara .
Ceres is a dwarf planet located in the asteroid belt between the orbits of mars and Jupiter. the radius of Ceres is 4.76 x 10^5 m. suppose an astronauts stands on the surface of Ceres and drops a 0.85 kg hammer from a height of 1.25 m. the hammer takes 3.0 to reach the ground.
a) determine the gravitational field strength of Ceres at this height.(ans 0.28 n/kg)
b) determine the mass of Ceres. (ans 9.4 x 10^20 kg)
c) determine the gravitational field strength of Ceres at an altitude of 150 km above its surface. (ans 0.16 N/kg)

a). The effective acceleration of gravity, g', is given by
(1/2)g'*t^2 = 1.25 m
g' = 2.5/9 = 0.28 m/s^2. (or N/kg)
b) G M/R^2 = 0.28 N/kg
G is the universal gravity constant. Look it up and solve for asteroid mass M.
c) g' falls inversely with the square of the distance from the center. Multiply the surface value, 0.28 N/kg, by (476 km/626 km)^2