Astronomers have observed a small, massive object at the center of our milky way galaxy. a ring of material orbits this massive object; the ring has a diameter of about 16 light-years and an orbital speed of about 130 km/s. for general problem-solving tips and strategies for this topic, you may want to view a video tutor solution of black hole calculations.
determine the mass m of the massive object at the center of the milky way galaxy. take the distance of one light year to be 9.461 x 1015m. express your answer in kilograms.

Ablock of mass m = 2.5 kg is attached to a spring with spring constant k = 710 n/m. it is initially at rest on an inclined plane that is at an angle of θ = 23° with respect to the horizontal, and the coefficient of kinetic friction between the block and the plane is μk = 0.19. in the initial position, where the spring is compressed by a distance of d = 0.16 m, the mass is at its lowest position and the spring is compressed the maximum amount. take the initial gravitational energy of the block as zero. a) what is the block's initial mechanical energy? b) if the spring pushes the block up the incline, what distance, l, in meters will the block travel before coming to rest? the spring remains attached to both the block and the fixed wall throughout its motion.

What are the theoretical properties of a gas at a temperature of 0 kelvin?

How does the amount of energy required to hold each proton and neutron in the nucleus compare to the energy released when they are removed?