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The energy equivalent of 1.0 kg of substance is ________.

Asked in GUJCET 2026 · Mass defect and binding energy

• (1) 9×10¹³ J
• (2) 9×10¹⁶ J
• (3) 3×10¹³ J
• (4) 9×10¹⁸ J

Step-by-step solution

Why the other options are wrong

• (1) 9×10¹³ J is the energy equivalent of 1 g. The mass here is 1.0 kg, a thousand times larger, so the energy is a thousand times larger too.
• (3) The mantissa 3 can only come from using c in place of c² — and even then mc=3×10⁸ J s m⁻¹, which is neither this number nor an energy.
• (4) 9×10¹⁸ squares only the power of ten and adds it on: (3×10⁸)²=9×10¹⁶, because 8+8=16.

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