Acommon pickup for an electric guitar consists of a coil of wire around a small permanent magnet, as described in figure 25.5. why will this type of pickup fail with nylon strings?

Guitar pickups are tiny coils with magnets inside them and they work via  the principal of electromagnetic inductance. The metal strings vibrate within the magnetic field of the pickup which generates an electrical current. Since nylon is not a metal, it will not cause fluctuations in that magnetic field. Hope this answer helps.

How is it possible that phylogenies based on sequences from nuclear genomes and organellar genomes (i.e., chloroplasts and mitochondria) from the same group of species yield phylogenetic trees with different branching orders?   answer :   the genome of the endosymbiont is more closely related to members of the group in which it originally evolved, while the nuclear genome of the engulfing organism has its own evolutionary trajectory.