Can someone explain why the M is assigned to be anticlockwise here ? 

[![1](https://i.stack.imgur.com/yIznY.jpg)](https://i.stack.imgur.com/yIznY.jpg)
When i assign it as clockwise , i will get -P(δ -v) , which is different from the author ... 
If i do so , then , all the sign will be different 
Can i do so ? Why ?

or the second example here , i can understand that M = -Pv , since M+Pv = 0 at either end when it's in equlibrium. 

P/s : I know the the sign convention of the bending moment of beam is positive when the beam upwards as shown ... 

For the first example , i gt M+P(∂-v) = 0 , so M = - P(∂-v) . 
I am not sure whether is my concept correct or not . 
[![2](https://i.stack.imgur.com/0YHl2.jpg)](https://i.stack.imgur.com/0YHl2.jpg)

[![3](https://i.stack.imgur.com/Bsuyp.jpg)](https://i.stack.imgur.com/Bsuyp.jpg)

[![4](https://i.stack.imgur.com/DWPXg.jpg)](https://i.stack.imgur.com/DWPXg.jpg)

[![5](https://i.stack.imgur.com/xJ36h.jpg)](https://i.stack.imgur.com/xJ36h.jpg)