An airplane is flying in air with a density of 1.29 kg/m3. A pressure gauge measures
the difference in pressure between a point on the nose of the airplane and a point on
the fuselage. The pressure on the nose is higher by 75.0 kPa. What is the speed of
the plane relative to the air?

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".