Class 11 Physics Chapter 1: Units and Measurement MCQs with answers
10 multiple-choice questions on Units and Measurement, each with its answer and the reason, written from the NCERT chapter. For school exams on the CBSE pattern, JEE Main and NEET, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter.
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Answer: (c) newton
The seven base units are the metre, kilogram, second, ampere, kelvin, mole and candela. The newton (kg m s⁻²) is a derived unit with a special name.
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Answer: (b) solid angle
Solid angle dΩ = dA/r² is measured in steradian (sr); plane angle is measured in radian, luminous intensity in candela and amount of substance in mole.
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Answer: (a) 0.00203 s
0.00203 s: the leading zeros only place the decimal point, so 2, 0, 3 count: three. 0.04050 kg has four (4, 0, 5 and the trailing zero after the decimal point); 3.070 m has four; 2.300 × 10³ g has four, since every zero in the base number of scientific notation is significant.
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Answer: (d) 2
In a number without a decimal point the trailing zeros are not significant, so only 3 and 6 count: two significant figures.
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Answer: (c) 4
0.5060 cm = 0.005060 m. A change of units does not change the significant figures: the leading zeros are not significant and 5, 0, 6, 0 are, giving four.
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Answer: (c) 2
In multiplication the result keeps as many significant figures as the factor with the fewest: 4.2 m has two. So 52.92 m² must be reported as 53 m², and the last two digits written, 9 and 2, are not justified.
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Answer: (c) It should be 22.2 g, since 3.1 g has only one decimal place.
The arithmetic sum is 22.177 g. In addition the result keeps as many decimal places as the least precise term, 3.1 g with one decimal place, so the total is 22.2 g. The significant-figure rule of (b) is the rule for multiplication and division, not for addition.
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Answer: (b) 6.38
The digit dropped is 5 and the preceding digit, 7, is odd, so it is raised by 1: 6.38. (Had the preceding digit been even, the 5 would simply be dropped.)
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Answer: (a) [M L⁻¹ T⁻²]
[Force]/[area] = [M L T⁻²]/[L²] = [M L⁻¹ T⁻²].
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Answer: (d) torque and work
Torque (force × perpendicular distance) and work (force × displacement) are both [M L² T⁻²]. Impulse is [M L T⁻¹] while force is [M L T⁻²]; pressure is [M L⁻¹ T⁻²]; angular momentum is [M L² T⁻¹] while linear momentum is [M L T⁻¹].