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NEET PHYSICSUNITS AND MEASUREMENTSEasy

Question

Which relation is wrong?

A

1 Calorie = 4.18 Joules

B

1 A˚=10−10\mathring{A} = 10^{-10} m

C

1 MeV = 1.6×10−131.6 \times 10^{-13} Joules

D

1 Newton = 10−510^{-5} Dynes

Step-by-Step Solution

  1. Analyze Option A: 1 calorie is defined as the heat energy required to raise the temperature of 1 g of water by 1∘1^{\circ}C. The mechanical equivalent of heat is approximately 4.184.18 J (or 4.1864.186 J). Thus, 1 Cal≈4.18 J1 \text{ Cal} \approx 4.18 \text{ J}. This relation is correct .
  2. Analyze Option B: The Angstrom (A˚\mathring{A}) is a unit of length used in atomic physics. 1A˚=10−10 m1 \mathring{A} = 10^{-10} \text{ m}. This relation is correct .
  3. Analyze Option C: 1 electron volt (eV) is 1.6×10−191.6 \times 10^{-19} J. Therefore, 1 Mega electron volt (MeV) = 106 eV=106×(1.6×10−19 J)=1.6×10−13 J10^6 \text{ eV} = 10^6 \times (1.6 \times 10^{-19} \text{ J}) = 1.6 \times 10^{-13} \text{ J}. This relation is correct .
  4. Analyze Option D: The Newton (N) is the SI unit of force, and the Dyne is the CGS unit of force.
  • 1 N=1 kg m s−2=(1000 g)(100 cm) s−2=105 g cm s−2=105 Dynes1 \text{ N} = 1 \text{ kg m s}^{-2} = (1000 \text{ g})(100 \text{ cm}) \text{ s}^{-2} = 10^5 \text{ g cm s}^{-2} = 10^5 \text{ Dynes}.
  • The option states 1 N=10−5 Dynes1 \text{ N} = 10^{-5} \text{ Dynes}, which is incorrect. The correct relation is 1 Dyne=10−5 N1 \text{ Dyne} = 10^{-5} \text{ N} .

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from UNITS AND MEASUREMENTS. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

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