A nuclear reactor uses control rods made of MCQ with Answer and Explanation

A nuclear reactor uses control rods made of
A. Cadmium
B. Uranium
C. Graphite
D. Heavy water
Answer: Option A
Solution (By JKSSB Mock Tests)
Cadmium or boron absorb neutrons to control chain reaction.

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Practice More Physics Questions

Question #1
The velocity-time graph of a particle moving in a straight line is shown. The displacement of the particle from t=0 to t=4s is: [Graph: triangle from (0,0) to (2,10) to (4,0)]
A. 30 m
B. 40 m
C. 10 m
D. 20 m

Correct Answer: Option D


Explanation:
Displacement = area under velocity-time graph. The graph forms a triangle with base 4 s and height 10 m/s. Area = ½ × base × height = ½ × 4 × 10 = 20 m. Since velocity is always positive, displacement equals distance travelled. Graphical analysis is powerful: area gives displacement, slope gives acceleration. This triangle represents motion with uniform acceleration followed by uniform retardation. Exam tip: For piecewise linear v-t graphs, calculate area of each geometric segment separately. Such graph-based questions assess conceptual clarity in motion analysis.

This question belongs to: Science Physics
Question #2
The universal law of gravitation states that the force between two masses is directly proportional to:
A. Product of the masses
B. Difference of the masses
C. Square of the distance between them
D. Sum of the masses

Correct Answer: Option A


Explanation:
Newton's law of gravitation: F = G·m₁m₂/r². Thus force is directly proportional to the product of the masses (m₁m₂) and inversely proportional to square of distance (r²). Option D incorrectly states 'directly proportional to square of distance' – it's inverse square. This fundamental law governs celestial mechanics. Memory tip: 'F ∝ m₁m₂ and F ∝ 1/r²'. Competitive exams often test precise wording of physical laws; distractors may reverse proportionality or misstate dependencies. Always recall the exact mathematical form.

This question belongs to: Science Physics
Question #3
A concave mirror forms a real, inverted, magnified image when object is
A. Between F and C
B. At infinity
C. Between P and F
D. At C

Correct Answer: Option A


Explanation:
Between F and C: image beyond C, magnified, inverted, real.

This question belongs to: Science Physics