Q26 of 42 Page 34

A mass of 2kg is suspended with thread AB (Fig. 5.5). 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?


To solve such questions, we first draw the free body diagram to see what forces are acting on the system. Here, we can see that the weight of the body is acting downwards and given by “mg”. The corresponding tension on the string AB is given by “T”. In addition to these forces, we apply a third force via string CD in the downward direction given by “F”. So,

T = F + mg


As the tension is the greatest force, given by the sum of the weight and the additional force applied, string AB will break.


More from this chapter

All 42 →
24

A woman throws an object of mass 500 g with a speed of 25 m s1.

(a) What is the impulse imparted to the object?


(b) If the object hits a wall and rebounds with half the original speed, what is the change in momentum of the object?


 25

Why are mountain roads generally made winding upwards rather than going straight up?

 27

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

 28

Two masses of 5 kg and 3 kg are suspended with help of massless inextensible strings as shown in Fig. 5.6. Calculate T1 and T2 when whole system is going upwards with acceleration = 2 m s2 (use g = 9.8 m s-2).