4. What is harder for the astronomer to measure: A galaxy's redshift (indicating recessional velocity) or its distance from Earth? Why? Explain your answer.

Aray of light traveling parallel to the principal axis of a concave mirror will be reflected through the mirror's

2kg of refrigerant 134a undergoes a polytropic process in a piston-cylinder assembly from an initial state of saturated vapor at 2 bar to a final state of 12 bar, 80 degree c. a)determine the work for the process in kj. b)sketch the process on a p-v diagram.

Determine the fraction of the magnitude of kinetic energy lost by a neutron (m1 = 1.01 u) when it collides head-on and elastically with a target particle at rest which is 21h (heavy hydrogen, m = 2.01 u).