B because 2800 divide by 40 is 20
Answer:
a) 0 J
b) W = nRTln(Vf/Vi)
c) ΔQ = nRTln(Vf/Vi)
d) ΔQ = W
Explanation:
a) To find the change in the internal energy you use the 1st law of thermodynamics:

Q: heat transfer
W: work done by the gas
The gas is compressed isothermally, then, there is no change in the internal energy and you have
ΔU = 0 J
b) The work is done by the gas, not over the gas.
The work is given by the following formula:

n: moles
R: ideal gas constant
T: constant temperature
Vf: final volume
Vi: initial volume
Vf < Vi, then W < 0 and the work is done on the gas
c) The gas has been compressed. Thus, its temperature increases and heat has been transferred to the gas.
The amount of heat is equal to the work done W
d)

- One common use of a convex mirror is as shaving mirror.
- One common use of convex mirror is as rear-view mirrors in automobiles vehicles.
<h3>What is a
concave mirror?</h3>
A concave mirror is also referred to as a converging mirror and it can be defined as a type of mirror that is designed and developed with a reflective surface that is typically curved inward and away from the source of light.
Basically, one common use of a convex mirror include the following:
<h3>What is a
convex mirror?</h3>
A convex mirror is also referred to as a diverging mirror and it can be defined as a type of mirror that is designed and developed with a reflective surface that typically bulges outward toward the source of light.
Basically, one common use of convex mirror is as rear-view mirrors in automobiles vehicles.
Read more on convex mirror here: brainly.com/question/24175067
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If both waves have the same wavelength, then the amplitude of
their sum could be anything between 1 cm and 9 cm, depending
on the phase angle between them.
If the waves have different wavelengths, then the resultant is a beat
with an amplitude of 9 cm.