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

Which of the following is a derived unit?
A. Newton
B. Candela
C. Second
D. Kilogram
Answer: Option A
Solution (By JKSSB Mock Tests)
Newton = kg·m/s², derived from base units. Kilogram, second, candela are base units. Derived units expressed in terms of base units. Joule, watt, pascal are also derived.

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Practice More Physics Questions

Question #1
Free fall: height h takes time t. Height 4h takes time:
A. 4t
B. t/2
C. t
D. 2t

Correct Answer: Option D


Explanation:
h = ½gt² ⇒ t ∝ √h. If h' = 4h, t' = √4 × t = 2t. Time doubles when height quadruples. Memory aid: 'Free fall: t ∝ √h; 4× height ⇒ 2× time'. Kinematics proportionality frequently tested in competitive exams.

This question belongs to: Science Physics
Question #2
Which of the following waves is longitudinal?
A. Sound waves in air
B. Light waves
C. Radio waves
D. Waves on a string

Correct Answer: Option A


Explanation:
Sound waves in air are longitudinal, particles vibrate parallel to wave propagation. Light and radio are electromagnetic, transverse. Waves on a string are transverse. In fluids, only longitudinal mechanical waves can propagate.

This question belongs to: Science Physics
Question #3
What is the physical meaning of the 'Work Function' of a metal in the context of the photoelectric effect?
A. The minimum energy required to eject an electron from the metal surface.
B. The electrical resistance of the metal when light shines on it.
C. The maximum kinetic energy of an emitted electron.
D. The total energy of an incident photon.

Correct Answer: Option A


Explanation:
In Einstein's photoelectric theory, electrons are bound to the metal lattice. The 'work function' (often denoted by Phi or W) is defined strictly as the absolute minimum thermodynamic work (energy) needed to overcome these binding forces and remove an electron from the surface into a vacuum. If incident photon energy (hf) is less than the work function, absolutely no emission occurs.

This question belongs to: Science Physics