I just watched the ending of video 6, where Prof. Lewin shows a string breaking below a weight and then above. He is able to control which string breaks because of the inertia of the weight, correct? If he pulls fast the bottom string breaks, slow the top string breaks...

Question

I just watched the ending of video 6, where Prof. Lewin shows a string breaking below a weight and then above.  He is able to control which string breaks because of the inertia of the weight, correct?  If he pulls fast the bottom string breaks, slow the top string breaks...

anonymous · Answer

I think you are correct

anonymous · Answer

I have the same doubt can anyone please clarify in a more detailed manner?

anonymous · Answer

When he pulled slowly, the upper string broke like we expected because of the regular arguments.
When he pulled quickly, it took some time to the force to "reach" the upper string because of the cube. By that time the force was so strong the lower one broke.