# NCERT Physics Class 11 Exemplar Ch 5 Laws of Motion Part 5 (For CBSE, ICSE, IAS, NET, NRA 2023)

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Q. 26. A mass of is suspended with thread AB (Fig.) . Thread CD of the same type is attached to the other end of 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?

Answer: because force on the upper thread will be equal to sum of the weight of the body and the applied force.

Q. 27. In the above given problem if the lower thread is pulled with a jerk, what happens?

Answer: If the force is large and sudden, thread CD breaks because as CD is jerked, the pull is not transmitted to AB instantaneously (transmission depends on the elastic properties of the body) .

Therefore, before the mass moves, CD breaks.

Q. 28. Two masses of are suspended with help of massless inextensible strings as shown in Fig. Calculate when whole system is going upwards with acceleration