The working principle of a Venturimeter, used to measure the flow rate of a liquid through a pipe, is primarily based on: MCQ with Answer and Explanation
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Question #1
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Half-life 5 days. Fraction remaining after 15 days:
Correct Answer: Option C
Explanation:
Number of half-lives n = 15/5 = 3. Fraction = (1/2)³ = 1/8. Exponential decay: N = N₀(1/2)^(t/T). Memory aid: 'After n half-lives: fraction = 1/2ⁿ'. Radioactivity calculation frequently tested in competitive exams with simple half-life arithmetic.
Number of half-lives n = 15/5 = 3. Fraction = (1/2)³ = 1/8. Exponential decay: N = N₀(1/2)^(t/T). Memory aid: 'After n half-lives: fraction = 1/2ⁿ'. Radioactivity calculation frequently tested in competitive exams with simple half-life arithmetic.
Question #2
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A wire of resistance R is stretched to double its length. Assuming volume remains constant, the new resistance is:
Correct Answer: Option D
Explanation:
Resistance R = ρL/A. Volume V = A·L constant. If L' = 2L, then A' = V/L' = V/(2L) = A/2. Thus R' = ρ(2L)/(A/2) = 4(ρL/A) = 4R. Resistance increases by factor of 4. Memory tip: 'Stretching wire: R ∝ L² when volume constant'. This proportional reasoning problem tests resistance concepts, frequently appearing in competitive exams. Always verify volume conservation assumption; if area changed independently, result would differ. This problem assesses understanding of geometric effects on electrical properties.
Resistance R = ρL/A. Volume V = A·L constant. If L' = 2L, then A' = V/L' = V/(2L) = A/2. Thus R' = ρ(2L)/(A/2) = 4(ρL/A) = 4R. Resistance increases by factor of 4. Memory tip: 'Stretching wire: R ∝ L² when volume constant'. This proportional reasoning problem tests resistance concepts, frequently appearing in competitive exams. Always verify volume conservation assumption; if area changed independently, result would differ. This problem assesses understanding of geometric effects on electrical properties.
Question #3
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The velocity of a body changes from 2 m/s to 10 m/s in 4 s. Distance covered in this time is (assuming constant acceleration)
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