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Units & Measurements

NEET Physics · 152 questions · Page 8 of 16 · Click an option or "Show Solution" to reveal answer

Q71
The energy required to break one bond in DNA is 10 -20 J. This value in eV is nearly :
A 0.6
B 0.06
C 0.006
D 6
Correct Answer
Option B
Solution
1eV=1.6times10−19J1eV = 1.6 \\times {10^{ - 19}}J
Q72
A screw gauge has least count of 0.01 mm and there are 50 divisions in its circular scale. The pitch of the screw gauge is :
A 0.25 mm
B 0.5 mm
C 1.0 mm
D 0.01 mm
Correct Answer
Option B
Solution

Least count = Pitch/No of divisions. 0.01 = Pitch/50. Pitch = 0.5 mm

Q73
Each side of a metallic cube of mass 5.580 kg is measured to the 9.0 cm. The density can be best expressed as X * 10^3 kg m^-3 where X is:
A 7.654
B 7.6
C 7.65
D 7.7
Correct Answer
Option B
Solution

Answer is 7.6 due to significant figures (2 sig figs from side measurement).

Q74
In a vernier calliper, 20 VSD coincide with 16 MSD (each division 1 mm). The least count is:
A 0.2 cm
B 0.01 cm
C 0.02 cm
D 0.1 cm
Correct Answer
Option C
Solution

LC = 1 MSD - 1 VSD = 1mm - (16/20)mm = 0.2mm = 0.02 cm

Q75
The speed of light in vacuum is taken as unity. If light takes 6 min 40 s to reach the Earth from the Sun, the distance between the Sun and the Earth in new unit is:
A 3×1083 \times 10^8
B 500
C 3×10103 \times 10^{10}
D 400
Correct Answer
Option D
Solution

Time t=400t=400 s. Distance d=vt=1×400=400d=v t=1 \times 400=400

Q76
Each side of a metallic cube of mass 5.580 kg is measured to the 9.0 cm. The density can be best expressed as X×103X \times 10^3 kg/m3 where X is:
A 7.654
B 7.6
C 7.65
D 7.7
Correct Answer
Option B
Solution

2 significant figures from side: 7.6

Q77
In a vernier calliper, 20 VSD coincide with 16 MSD (each division 1 mm). The least count is:
A 0.2 cm
B 0.01 cm
C 0.02 cm
D 0.1 cm
Correct Answer
Option C
Solution

LC = 1 - 16/20 = 0.2 mm = 0.02 cm

Q78
A physical quantity P=a3b2/cdP=a^3 b^2 / c \sqrt{d}. Percentage errors in a,b,c,d are 1%,3%,2%,4%. Error in P is:
A 13%13\%
B 15%15\%
C 10%10\%
D 2%2\%
Correct Answer
Option A
Solution

3(1)+2(3)+2+0.5(4)=13%

Q79
The dimensions of (mu0varepsilon0)−1/2(\\mu_0 \\varepsilon_0)^{-1/2} are
A [L1/2T−1/2][L^{1/2}T^{-1/2}]
B [L−1T][L^{-1}T]
C [LT−1][LT^{-1}]
D [L1/2T1/2][L^{1/2}T^{1/2}]
Correct Answer
Option C
Solution

(mu0varepsilon0)−1/2=c(\\mu_0 \\varepsilon_0)^{-1/2} = c, speed of light = [LT−1][LT^{-1}]

Q80
Planck's constant (h), speed of light (c) and Newton's gravitational constant (G). Which combination has dimension of length?
A hG/c3/2\sqrt{hG}/c^{3/2}
B hG/c5/2\sqrt{hG}/c^{5/2}
C hc/G\sqrt{hc/G}
D Gc/h3/2\sqrt{Gc/h^{3/2}}
Correct Answer
Option A
Solution

Dimensional analysis gives p=r=1/2, q=-3/2. L = sqrthG/c3/2\\sqrt{hG}/c^{3/2}

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