Answer:
C. -12 ab
Explanation:
The restoring force on a spring is given by Hooke's law:

where
k is the spring constant
x is the stretched (or compressed) displacement of the spring
In this problem we have:
k = 4a
x = 3b
Substituting into the equation, we find:

And the negative sign means that the direction of the force (negative) is opposite to the direction of the displacement (positive).
The energy stored in the membrane is 
Explanation:
The capacitance of a parallel-plate capacitor is given by

where
k is the dielectric constant of the material
is the vacuum permittivity
A is the area of the plates
d is the separation between the plates
For the membrane in this problem, we have
k = 4.6


Substituting, we find its capacitance:

Now we can find the energy stored: for a capacitor, it is given by

where
is the capacitance
is the potential difference
Substituting,

Learn more about capacitors:
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The combined-gas law relates which temperature, pressure and volume.
Temperature=T
Pressure=P
Volume=V
(P₁*V₁) / T₁=(P₂*V₂) / T₂
D. Temperature, pressuere and volume.
<h2>
Answers:</h2>
-The first direct detection of gravitational waves came in 2015
-The existence of gravitational waves is predicted by Einstein's general theory of relativity
-Gravitational waves carry energy away from their sources of emission
<h2>
Explanation:</h2>
Gravitational waves were discovered (theoretically) by Albert Einstein in 1916 and "observed" for the first time in direct form in 2015 (although the results were published in 2016).
These gravitational waves are fluctuations or disturbances of space-time produced by a massive accelerated body, modifying the distances and the dimensions of objects in an imperceptible way.
In this context, an excellent example is the system of two neutron stars that orbit high speeds, producing a deformation that propagates like a wave,<u> in the same way as when a stone is thrown into the water</u>. So, in this sense, gravitational waves carry energy away from their sources
.
Therefore, the correct options are D, E and F.
Mass is how heavy is it, weight is the size both are the same