Problem 4 Water is flowing in a pipe with varying cross-sectional area. At the point A, where the cross
sectional area of the pipe is 0.0700 m2
, the velocity of the water is 3.50 m/s. Compute:
a) The speed of the water at point B, where the cross-sectional area of the pipe is 0.105
m2
;
b) The speed of the water at point C, where the cross-sectional area of the pipe is 0.0470
m2
;
c) The rate at which water flows in the pipe (in m3/s);
d) If point B is 10.0 m below point C, what is the difference in pressure between point B
and point C?

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.