NEET Free Online Mock Test - 2019

NEET Physics  Units & Measurements  Practice Q & A

1. A screw gauge with a pitch of 0.5 mm and a circular scale with 50 divisions is used to measure the thickness of a thin sheet of Aluminium. Before starting the measurement, it is found that when the two jaws of the screw gauge are brought in contact, the 45th division coincides with the main scale line and that the zero of the main scale is barely visible. What is the thickness of the sheet if the main scale reading is 0.5 mm and the 25th division coincides with the main scale line?

0.80 mm 0.70 mm 0.50 mm 0.75 mm

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2. If energy (E), velocity (V) and time (T) are chosen as the fundamental quantities, the dimensional formula of surface tension will be

[E V–2 T–1] [E V–1 T–2] [E V–2 T–2] [E–2 V–1 T–3]

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3. Which of the following units denotes the dimensions ML2/Q2, where Q denotes the electric charge?

Weber (Wb) Wb/m2 Henry (H) H/m2

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4. If n denotes a positive integer, h the Planck’s constant, q the charge and B the magnetic field, then the quantity $\dfrac{nh}{2\pi qB}$ has the dimension of

area length speed acceleration

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5. The dimension of magnetic field in M, L, T and C (Coulomb) is given as

MLT–1C–1 MT2C–2 MT–1C–1 MT–2C–1

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6. The period of oscillation of a simple pendulum is $T = 2\pi\sqrt{\dfrac{L}{g}}$. Measured value of L is 20.0 cm known to 1 mm accuracy and time for 100 oscillations of the pendulum is found to be 90 s using a wrist watch of 1 s resolution. The accuracy in the determination of g is

2% 3% 1% 5%

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7. A screw gauge gives the following reading when used to measure the diameter of a wire.
Main scale reading : 0 mm
Circular scale reading : 52 divisions
Given that 1 mm on main scale corresponds to 100 divisions of the circular scale.
The diameter of wire from the above data is

0.005 cm 0.52 cm 0.052 cm 0.026 cm

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8. A wire of length l = 6 ± 0.06 cm and radius r = 0.5 ± 0.005 cm and mass m = 0.3 ± 0.003 gm. Maximum percentage error in density is

4 2 1 6.8

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9. In the expression for Boyle’s law, the product ‘PV’ has dimensions of

force impulse energy momentum

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10. In an experiment four quantities a, b, c and d are measured with percentage error 1%, 2%, 3% and 4% respectively. Quantity P is calculated as follows : $P = \dfrac{a^3b^2}{cd}$. % error in P is

14% 10% 7% 4%

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