Mersenne's laws govern the construction and operation of string instruments, such as pianos and harps, which must accommodate the total tension force required to keep the strings at the proper pitch. Lower strings are thicker, thus having a greater mass per length. They typically have lower tension.
The principles formulated by Mersenne dictate the design and functioning of stringed musical instruments, including pianos and harps, which need to withstand the total tension required to produce the correct pitch. Thicker strings typically possess a higher mass-to-length ratio, leading to reduced tension.