A mass of 2 kg is suspended with thread AB (Figure). Thread CD of the same type is attached to the other end of 2 kg mass. Lower thread is pulled gradually, harder and harder in the downward direction so as to apply force on AB. Which of the threads will break and why?
The force on CD = force applied at D downward,
whereas the Force on AB = Force F along with force due to mass 2 kg downward.
Thus, the force on AB is more than fore at D by 2 kg, which will lead to the breakup of thread AB.
Hence, thread AB will break.