Answer:
Thermal energy of an isolated system changes with time If the mechanical energy of that system is constant according to the first law of thermodynamics, which states that thermal energy of an isolated system can still change as long as the total energy of that system does not change.
Explanation:
Answer: The field lines bend away from the second positive charge
Explanation: opposite attracts, same repulse
The correct answer is D. I alread took this test.
Answer:

Explanation:
P = Power = 50 kW
n = Number of photons per second
h = Planck's constant = 
= Frequency = 781 kHz
r = Distance at which the photon intensity is i = 1 photon/m²
Power is given by

Photon intensity is given by

The distance is 
Explanation and Examples
let the mass of the compressor be
mass (m):
height in x axis is (h1)
height in y axis be (h2):
Height difference: h2-h1
displacement x force:
mass x gravity x height
(m)*9.8*(height difference) = ___ J
Since gravity is forcing down, it would be negative!
Put the values that you require and get the answer.