What Causes Cords to Break Under Tension?

[gurparwaan]

a heavy block of mass m is supported by cord cattatched to ceiling and another cord d s attatched to bottom of the block .if a sudden jerk is given to d,then what happens:-
1)c breaks
2)d breaks
3)both breaks
4)none of them breaks

 

[Owen-]

Well it depends on the strength of the impulse, the cords being identical and if they are extensible, but assuming the obvious things here..

The top cord has both the force of the impulse and the force of the weight acting on it, whereas only the force of the impulse affects the bottom cord.

Hope that helps

 

[gurparwaan]

Well it depends on the strength of the impulse, the cords being identical and if they are extensible, but assuming the obvious things here..

The top cord has both the force of the impulse and the force of the weight acting on it, whereas only the force of the impulse affects the bottom cord.

Hope that helps

but what do u think is the ans

 

[Doc Al]

What do you think and why?

Hint: How is a sudden jerk different than a steadily increasing pull?

 

[gurparwaan]

What do you think and why?

Hint: How is a sudden jerk different than a steadily increasing pull?

sudden jerk creates an impulse but normal pull does not.
but still i am not getting the question

 

[Doc Al]

A steadily increasing pull on the lower cord allows the force to be transmitted.

If you slowly increase the pull on the lower cord to a tension T, what's the tension in the upper cord? (Assume the block has a weight W.) Assuming both cords have the same breaking strength, which will break first?

Once you understand that case, then we can deal with the sudden jerk case.