Two piano strings are supposed to be vibrating at 220 hz, but a piano tuner hears three beats every 2.5 s when they are played together.
(a) if one is vibrating at 220.0 hz, what must be the frequency of the other (is there only one answer)?
(b) by how much (in percent) must the tension be increased or decreased to bring them in tune?

Ablock of mass m = 2.5 kg is attached to a spring with spring constant k = 740 n/m. it is initially at rest on an inclined plane that is at an angle of theta= 26 with respect to the horizontal, and the coefficient of kinetic friction between the block and the plane is uk = 0.17. in the initial position, where the spring is compressed by a distance of d = 0.16 m, the mass is at its lowest position and the spring is compressed the maximum amount. take the initial gravitational energy of the block as zero. the block's initial mechanical energy is 9.472 j.b. if the spring pushes the block up the incline, what distance l in meters will the block travel before coming to rest? the spring remains attached to both the block and the fixed wall throughout its motion.