What is the difference between a battery losing charge (discharging) and a capacitor losing charge (discharging)?

The capacitor takes the charge from the battery but the electromotive force EMF of the battery remains same. But, during discharging, the internal resistance of the battery decreases because the charge moves out of the battery to the capacitor.
But, when the capacitor discharges its emf,  decreases with time.

Distance^2= yellow line ^2 (see picture) = 30^2 + 49^2so distance = squareroot of (300^2 +49^2)i dont know if this is how to solve it, but i cnt think of another way

    5.5 n======    assuming that      we have      m = 0.145 kg    a = 38 m/s²therefore    5.51 n, but two significant figures.final answer: 5.5 n