What happens when voltage doubles from 15v to 30v

If the voltage doubles, the current also doubles for the same resistance. If the circuit is liner, and you have a single independent voltage source, doubling this voltage source will double the current and quadruple the power. If the circuit is nonlinear, like a circuit with diodes or transistors, in general doubling the voltage doesn't double the current nor quadruples the power.

explanation:

as the height from which the ruler was dropped increased, the speed of the ruler at ryan's hand increased.