Which one of the following frequencies of a wave in the air can be heard as an audible sound by the human ear?
a. 100,000 hz
b. 10 hz
c. 1,000 hz
d. 0.10 hz

Suppose while hauling rocks, you accidentally drop one. it breaks apart in flat, planar sections. what type of rock did you just drop? 20 points

Aballoon is rising vertically upwards at a velocity of 10m/s. when it is at a height of 45m from the ground, a parachute bails out from it. after 3s he opens his parachute and decelerates ata a constant rate 5m/s.when. (a) what was the height of the parachutist above the ground when he opened his parachute? (b)how far is the parachutist from the balloon at t=3s? (c)with what velocity does the parachutist hit the ground? (d)after how long does the parachutist hit the ground after his exist from the balloon?

An object is placed in front of a concave mirror between the pole and the focus of the mirror, what is the nature of the image formed by the mirror