Recent findings in astrophysics suggest that the observable universe can be modeled as a sphere of radius r = 13.7 × 109 light-years = 13.0 × 1025 m with an average total mass density of about 1 × 10-26 kg/m3. only about 4% of total mass is due to "ordinary" matter (such as protons, neutrons, and electrons). part a estimate how much ordinary matter (in kg) there is in the observable universe.

Ateam of astronauts is on a mission to land on and explore a large asteroid. in addition to collecting samples and performing experiments, one of their tasks is to demonstrate the concept of the escape speed by throwing rocks straight up at various initial speeds. with what minimum initial speed vesc will the rocks need to be thrown in order for them never to "fall" back to the asteroid? assume that the asteroid is approximately spherical, with an average density p 3.84 x108 g/m3 and volume v 2.17 x 1012 m3 recall that the universal gravitational constant is g 6.67 x 10-11 n m2/kg2

Ahowler monkey is the loudest land animal and, under some circumstances, can be heard up to a distance of 4.6 km. assume the acoustic output of a howler to be uniform in all directions and that the threshold of hearing is 1.0 × 10-12 w/m2. what is the acoustic power emitted by the howler

How is sound energy produced a. vibrating objects b. objects being heated c. temperature differences d. stationary objects