Experiment in dynamics or Newton's laws During my physics class the teacher demonstrated an experiment to us, the schematic for which is provided below.

The teacher said that if we pull the rope slowly than the rope will tear at connection A, but if we pull the rope instantly or with a really high speed it will tear at connection B.
Why is that happening? Can someone please give me an in-depth explantaion and explain me this mathematically using Newton's laws?
 A: When you pull slowly the tension is greatest in the top string and that is where is breaks.  
Pulling really fast means that you pull the bottom of the bottom string a certain distance but the top of the bottom string hardly moves at all because it is connected to a large mass whose acceleration will be small.
This means that the pull on the top string is very small because the bottom of the top string will move hardly at all.
So the bottom string breaks in this case as the tension in the bottom string is larger than in the top string..
A: *

*The rope with the highest tension is going to break first.

*The ropes must have some flexibility for it to work, allowing the ball to accelerate downwards when pulled.

*With slow pulling the acceleration of the ball is negligible and the balance of forces make the top rope carry a higher tension since you have to add the weight of the ball to the pulling force.

*When the pulling force is higher than the weight of the ball, the inertial forces (acceleration) of the ball resist motion and act upwards, which reduces the tension on the top rope.

*At some point, the tension on the bottom is going to be higher than the top rope because the inertial forces add to the bottom.


In order to solve this yourself, please do a free body diagram that replaces the ropes with forces and balance things out to see what happens. For case a) ignore the acceleration of the ball, and force case b) include it.
