What Causes Cords to Break Under Tension?

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The discussion focuses on the mechanics of cord tension when a sudden jerk is applied to a lower cord supporting a block. It highlights that the top cord experiences both the impulse force and the weight of the block, while the bottom cord is only affected by the impulse. The impact of a sudden jerk differs from a steadily increasing pull, as the former creates an impulse that can exceed the cords' breaking strength. Participants are encouraged to analyze the tension dynamics in both scenarios to determine which cord would break first. Understanding these principles is crucial for predicting the outcome of tension-related failures in such setups.
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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
 
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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
 


Owen- said:
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
 


What do you think and why?

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


Doc Al said:
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
 


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.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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