Why does a vibrating simple pendulum not produce any sound

In raising a 6200-n piano with a pulley system, the movers note that, for every 2.2 m of rope pulled down, the piano rises 0.12 m . ideally, find the force required to lift the piano.

The earth remains in orbit around the sun due to the force of gravity. how does the force of gravity exerted by the sun on the earth compare to the force of gravity exerted by the earth on the sun?

Light traveling in a medium with a refractive index 1.19 is incident on a plate of another medium with index of refraction 1.79. at what angle of incidence is the reflected light fully polarized?