Two springs with equal spring constants $k$ are connected first in series (one after the other) and then in parallel (side by side) with an object hanging from the bottom of the combination. What is the effective spring constant of the two different arrangements? In other words, what would be the spring constant of a single spring that would behave exactly as (a) the series combination and (b) the parallel combination? Ignore the weight of the springs. [Hint for (a): each spring stretches an amount $x=F / k,$ but only one spring exerts a force on the hanging object. Hint for (b): each spring exerts a force $F=k x$ on the object when each spring stretches a distance $x .]$