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    				| 1. | Two blocks of masses 1 kg and 2kg are connect by a metal wire going over a smooth pulley as shown in figure. The breaking stress of the metal is `2xx10^9m^-2`. What should be the minmum radius of the wire used if it is not to break? Take `g=10ms^-2` | 
| Answer» The stress in the wire `=Tension/(Area of cross section)` To avoid breaking, this stress should not exceed the breaking stress. Let the tension in the wire be T. The equations of motion of the two blocks are `T-10N=(1kg)a` `and 20N-T=(2kg)a` ElimiN/Ating a from these equations `T=(40/3)N` `The stress=((40/3)N)/(pir^2)` If the minimum radius needed to avoid breaking is r, `2xx10^9 N/m^2=((40/3)N)/(pir^2)` `solving this `r=4.6xx10^-5m`. | |