Assume a certain adult requires 2.4 × 102 ml of pure oxygen per minute and assume inhaled air contains 20.0 percent oxygen by volume and exhaled air is 16.0 percent. (also, assume that the volume of inhaled air is equal to that of the exhaled air.) if the person breathes 12.0 times every minute, what is the volume of air per breath?

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".