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Two wires as shown in the figure below are made of steel and have a breaking stress of 12×10⁸ N m⁻². The upper wire hangs from the ceiling and carries a 30 kg block; the lower wire hangs from that block and carries a 10 kg block, below which the pan is attached. The area of cross-section of the upper wire is 0.008 cm² and of the lower wire is 0.004 cm². The maximum mass that can be added to the pan without breaking any wire is ______ kg. (Take g=10 m s⁻²)

Asked in JEE Main 5th April 1st Shift 2026 · Breaking stress and maximum load

• (1) 56
• (2) 38
• (3) 96
• (4) 5.6

Step-by-step solution

Why the other options are wrong

• (1) 56 kg is the limit set by the upper wire alone, 96-30-10; it comes from testing only the thicker wire and missing that the thinner lower wire fails first, at 38 kg.
• (3) 96 kg is the total mass the upper wire can support, (12×10⁸×8×10⁻⁷)/(10); it comes from forgetting to subtract the 30 kg and 10 kg blocks already hanging.
• (4) 5.6 kg is option 1 with a decimal slip in the area conversion, taking 0.008 cm² as 0.008×10⁻⁶ m² instead of 0.008×10⁻⁴ m².

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