Synchronous communications satellites are placed in a circular orbit that is 3.59* 10^7 m above the surface of the earth. What is the gravitational field strength at this height? (0.223 m/s^2) Gravitational field strength = g = GM/r^2 (the force it would exert per kilogram.)

Iron reacts with sulfur to form iron sulfide. if 60 grams of iron reacts with sulfur to produce 90 grams of iron sulfide, how much sulfur has been used in the chemical reaction?

When the force acting on an object points at least partially in the direction of the motion the work done is considered to be negative

The atoms in a nickel crystal vibrate as harmonic oscillators with an angular frequency of 2.3 × 1013 rad/s. the mass of a nickel atom is 9.75 × 10-26 kg. what is the difference in energy between adjacent vibrational energy levels of nickel? (h = 6.626 × 10-34 j • s, , 1 ev = 1.60 × 10-19 j)