Which of the following is a derived unit in SI system? MCQ with Answer and Explanation

Which of the following is a derived unit in SI system?
A. Ampere
B. Kelvin
C. Mole
D. Newton
Answer: Option D
Solution (By JKExamLibrary)
Newton is a derived unit representing force, defined as kg·m/s². Kelvin (temperature), Ampere (current), and Mole (amount of substance) are fundamental SI units. Derived units are combinations of fundamental units through physical relationships. Newton comes from Newton's second law: F = ma. Memory aid: Remember the seven fundamental SI units: meter, kilogram, second, ampere, kelvin, mole, candela. All others like newton, joule, watt are derived. This distinction is essential for unit conversion questions in competitive exams.

This question belongs to: Science Physics

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Question #1 Report Error
Which SI prefix represents 10⁻⁶?
A. micro
B. pico
C. nano
D. milli

Correct Answer: Option A


Explanation:
Micro (μ) denotes 10⁻⁶ in SI system. Nano = 10⁻⁹, pico = 10⁻¹², milli = 10⁻³. Standard prefixes: kilo(10³), milli(10⁻³), micro(10⁻⁶), nano(10⁻⁹). Memory aid: 'Micro = millionth; μm = micrometer = 10⁻⁶ m'. Frequently tested for unit conversion proficiency in competitive exams.

This question belongs to: Science Physics
Question #2 Report Error
Weight of an object on the Moon is about _____ of its weight on Earth.
A. 1/8
B. 1/4
C. 1/2
D. 1/6

Correct Answer: Option D


Explanation:
Moon's gravity is about 1/6th of Earth's gravity. So weight (mg) is 1/6 of Earth weight. Mass remains same. g_moon ≈ 1.62 m/s², g_earth ≈ 9.8 m/s², ratio ≈ 1/6. Common fact in space science.

This question belongs to: Science Physics
Question #3 Report Error
Carnot efficiency η = 1 - T₂/T₁. If T₁=600K, T₂=300K, η is:
A. 50%
B. 25%
C. 75%
D. 100%

Correct Answer: Option A


Explanation:
η = 1 - 300/600 = 1 - 0.5 = 0.5 = 50%. Maximum possible efficiency for given temperatures. Memory aid: 'η_Carnot = 1 - T_cold/T_hot; always < 100%'. Thermodynamics calculation frequently tested in competitive exams.

This question belongs to: Science Physics