Thank you so much Ravi😇

Listen carefully

its because he assumed that his CONTROL VOLUME has constant volume. so when density is invariable for the fluid, the mass inside is fixed.

why??

In simple terms.. Heat q is an inexact differential. It means there is no such function Q which can be written as Q=∫đq.No such function of Q exists. If you need a complete detailed explanation, I suggest you to check this link farside.ph.utexas.edu/teaching/sm1/lectures/node36.html

a late reply from a present college student but yes you're right

ये लोग चुतिया होते है. फुकट का ज्ञान लेने की भी औकात नही होती है ऐसों की. फुकट का ज्ञानसागर बह रहा है, किंमत नही है.

Fixed amount of matter: fixed amount of mass [kg]. The size of the system can change, but the mass is the same. Fixed size: fixed amount of volume [m^3]. The mass inside the fixed volume can change. Like putting more stuff into a box, where the box is your fixed volume. Examples: Fixed amount of matter: Think of a closed balloon. If the air inside the balloon heats up, it expands (energy flow + change of boundary) but there is still the same amount of matter inside the balloon, because mass doesn't flow in or out of the closed balloon. Fixed size: you choose your control volume, for example the room you are in. You can open a door and windows, and air, insects and other stuff can flow through the room (boundaries of your control volume).

😂

*Viscosity He was summing up all the work done on C.V, C.S included

Vy is the velocity component of vn in y direction

A control volume system is the system in which only volume of the system is fixed so mass can come and go out of the system it may be case for steady state that mass flow in and out are same but mass will flow out of the system so there is mass continuous mass and energy interaction for control volume and hence it is called the Open System.

sunita kumari Its a system of fixed mass with fixed identity.