Q5 of 29 Page 65

A rigid bar of mass M is supported symmetrically by three wires each of length l. Those at each end are of copper and the middle one is of iron. The ratio of their diameters, if each is to have the same tension, is equal to

Since, all the wires need to have same tension and we know that Young’s modulus of the wires shall be the ratio of the tension they experience to their area of cross – section, we have



Similarly




Equating tensions, we get



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