Molly Music is sitting in the audience at a concert. When the concert begins, the band, Truth
Hertz, warms up by singing notes and the sound plays over two speakers. Molly is sitting at
the position shown and the speakers are separated by 15.0 m.
i. Find the path difference of the sound where Molly is sitting. [3 points]
ii. What are the lowest three frequencies for which Molly hears loud sound? [4 points]

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

The ultracentrifuge is an important tool for separating and analyzing proteins. because of the enormous centripetal accelerations, the centrifuge must be carefully balanced, with each sample matched by a sample of identical mass on the opposite side. any difference in the masses of opposing samples creates a net force on the shaft of the rotor, potentially leading to a catastrophic failure of the apparatus. suppose a scientist makes a slight error in sample preparation and one sample has a mass 10 mg larger than the opposing sample. if the samples are 12 cm from the axis of the rotor and the ultracentrifuge spins at 70,000 rpm, what is the magnitude of the net force on the rotor due to the unbalanced samples? ( be thorough on your answer)

What is friction? how does it affect the motion of an object?