Exams › JEE Main › Physics

A vertical steel rod of cross-sectional area 16 cm² acts in parallel with two brass rods, each of cross-sectional area 10 cm², and together they support a load of 5000 kg. The rods are arranged so that all three undergo the same strain. Taking Y for steel = 2.0*10⁶ N/cm² and Y for brass = 1.0*10⁶ N/cm² and g = 9.8 m/s², what is the stress developed in the steel rod?

1. 1884.6 N/cm²
2. 942.3 N/cm²
3. 3062.5 N/cm²
4. 1531.3 N/cm²

Correct answer: 1884.6 N/cm²

Solution

Because the rods share the load and deform equally (same strain), the stress in each is proportional to its Young's modulus, so steel carries twice the stress of brass. Combining this with the load-balance equation over the total cross-sectional areas (16 cm² of steel and 2*10 = 20 cm² of brass) and the total weight 5000*9.8 = 49000 N gives a steel stress of about 1884.6 N/cm².

Related JEE Main Physics questions

• Select the incorrect statement.
• A steel wire has length l and cross-sectional area A. When a certain load is applied, it elongates by 1 cm. If the same load is now applied to another steel wire made of the same material, having twice the length and half the cross-sectional area, what will be its extension?
• For common metals such as aluminium and copper, which sequence correctly represents the relative magnitudes of the elastic moduli?
• A steel sheet fails under a shear stress of 3.5 × 10⁸ N m⁻². The approximate force required to punch a circular hole of diameter 1 cm through a steel plate 0.3 cm thick is:
• A copper wire of fixed volume V is stretched out to a length l. If a constant force F is applied to this wire and it elongates by Δl, which of the following plots would be a straight line?
• A material has Poisson’s ratio equal to 0.5. When a tensile force is applied to a wire made of this material, its cross-sectional area decreases by 4%. The corresponding percentage increase in its length is:

⚔️ Practice JEE Main Physics free + battle 1v1 →