Answer:
The system loses 90 kJ of heat
Explanation:
We can answer the question by using the 1st law of thermodynamics, which states that:

where
is the change in internal energy of the system
is the heat absorbed by the system (positive if absorbed, negative if released by the system)
is the work done by the system (positive if done by the system, negative if done by the surrounding on the system)
In this problem, we have:
is the work done (negative, because it is done by the surrounding on the system)
is the increase in internal energy
Using the equation above, we can find Q, the heat absorbed/released by the system:

And the negative sign means that the system has lost this heat.
Answer:
20 m/s westward
Explanation:
Taking eastward as positive direction, we have:
is the velocity of Bill with respect to Amy (which is stationary)
is the velocity of Carlos with respect to Amy
Bill is moving 5 m/s eastward compared to Amy at rest, so the velocity of Bill's reference frame is

Therefore, Carlos velocity in Bill's reference frame will be

and the direction will be westward (negative sign).
A because of the resistors are four in this options first option is multiplied by 4
Isotopes refer to different atoms of the same element (i.e. same number of protons) that differ in the number of neutrons they have (giving them different atomic weights). Atomic weight is the sum of protons and neutrons (each contributes 1 atomic mass unit).
Carbon has 6 protons by definition. If you have a carbon-13 atom (the 13 referring to its mass), the atom has 13 - 6 = 7 neutrons. Since it's neutral, protons = electrons, so there are also 6 electrons.
Sulfur has 16 protons by definition. If you have a sulfur-32 atom, the atom has 32 - 16 = 16 neutrons. Since it's neutral, protons = electrons, so there are also 16 electrons.