Object mass40kg is suspended by light string from ceiling of lift of mass200kgThe string breaks if suffers a tension700NFind greatest tension the lift cable if string's intactAns equals4200N n 440N Y?

Answer 1

For simplicity let us assume the acceleration due to gravity to be 10 m/s2

The max force on the string is be 700 N. ie with mass of 40 kg, the acceleration max has be 700/40 ie 35/2 m/s2

The g value is 10 so the excess acceleration that is getting added is 35/2 -10 ie 15/2 m/s2.

This acceleration is due to the acceleration of the ascending lift. Hence the tension on the lift cable will be got by the product of the mass of the lift and its acceleration.

So it comes to be 1500 N. Already a tension which equals to the weight of the lift namely 2000 N is there. Hence the total tension becomes 3500N. I can't understand why the ans seems equal to 4200 N and 440 N as you have mentioned in the problem.

Answer 2

If the string breaks at 700N, then the lift cable can have a maximum tension of 700N before it breaks. Therefore, the answer is 700N. The values of 4200N and 440N are incorrect for this scenario.