Air resistance is the answer
Answer:

Explanation:
<u>Net Forces and Acceleration</u>
The second Newton's Law relates the net force
acting on an object of mass m with the acceleration a it gets. Both the net force and the acceleration are vector and have the same direction because they are proportional to each other.

According to the information given in the question, two forces are acting on the swimming student: One of 256 N pointing to the south and other to the west of 104 N. Since those forces are not aligned, we must add them like vectors as shown in the figure below.
The magnitude of the resulting force
is computed as the hypotenuse of a right triangle


The acceleration can be obtained from the formula

Note we are using only magnitudes here



The energy stored by a system of capacitors is given by

where Ceq is the equivalent capacitance of the system, and V is the voltage applied.
In the formula, we can see there is a direct proportionality between U and C. This means that if we want to increase the energy stored by 4 times, we have to increase C by 4 times, if we keep the same voltage.
Calling

the capacitance of the original capacitor, we can solve the problem by asking that, adding a new capacitor with

, the new equivalent capacitance of the system

must be equal to

. If we add the new capacitance X in parallel, the equivalent capacitance of the new system is the sum of the two capacitance

and since Ceq must be equal to 4 C1, we can write

from which we find