In the given diagram:
If the string in the entire system is the same and is assumed to be massless, then why is the tension in the string between objects $M_1$ and $M_2$ different from the tension in the string between objects $M_2$ and $M_3$? $M_2$ and $M_3$ have equal masses and $M_1$ is assumed to be moving downwards with a uniform velocity.
I am assuming the reason is because , even though the string is the same yet the force by which $M_1$ pulls onto $M_2$ is not the same as the force by which $M_2$ pulls onto $M_3$ because the weights of $M_1$ and $M_2$ are not equal. Is this right?