Liquid kerosene flows through a venturi meter, as shown in fig. p1.36. the pressure of the kerosene in the pipe supports columns of kerosene that differ in height by 12 cm. determine the difference in pressure between points a and b, in kpa. does the pressure increase or decrease as the kerosene flows from point a to point b as the pipe diameter decreases? the atmospheric pressure is 101 kpa, the specific volume of kerosene is 0.00122 m3/kg, and the acceleration of gravity is g 5 9.81 m/s2.

We know 
Pa=Patm+dgh+dgl
 here Pa is pressure in pipe with higher level of liquid
 Patm is atmospheric pressure
 d is density
 g is gravitational constant
 h is height of lower liquid
 l is difference is height of higher liquid
 So Pb= Patm+dgh
 here Pb is pressure lower level pipe
 so 
 Pdiff=Pb-Pa
 Pdiff=-dgl
 We know 
 Density of kerosene is the reciprocal of it’s specific volume
 so d=1/v=1/0.00122=820kg/m3
 as g=9.81 and l=12cm
 Pdiff= - 820*9.81*12/100
 Pdiff = -965.304 Pa

 Negative sign shows pressure decreases as the kerosene flows from point A
to point B as the pipe diameter decreases.

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.