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Under Graduate Entrance Exams NEET Entrance Exam Physics TEST : 129

Under Graduate Entrance Exams NEET Entrance Exam # Physics System of Particles and Rotational Motion Prepare / Learn

Q1. A thin circular ring of mass M and radius R is rotating about its central axis with angular velocity. Four point objects each of mass m are attached gently to the opposite ends of two perpendicular diameters, the angular velocity of the ring is given by

A. MM+4m⋅ω

B. M+4mM⋅ω

C. M−4mM+4m⋅ω

D. MM+m⋅ω

Answer : Option A
Explaination / Solution:

Let $ω$ be the angular velocity of the Ring of Mass M , thus the moment of inetia about given axis is I1 = $M R^{2}$ and the four point objects are genlty placed at perpendicular diameters at opposite end, so thus the distance of each object from axis of rotation is R, so total moment of inetia of ring and four objects is I2 = $M R^{2} + 4 m R^{2}$

According to law of conservation of angular momentum I1 $ω$ = I2 $ω$ 2 , So on solving $ω_{2} = (\frac{M R^{2}}{M R^{2} + 4 m R^{2}}) ω$ = $\frac{M}{M + 4 m} \cdot ω$

Under Graduate Entrance Exams NEET Entrance Exam # Physics Mechanical Properties of Fluids Prepare / Learn

Q2. It is easier to spray water to which soap is added, because

A. Addition of soap to water increases its density

B. Addition of soap to water makes surface tension of water zero

C. Addition of soap to water decreases surface tension of water

D. Addition of soap to water increases surface tension of water

Answer : Option C
Explaination / Solution:

Addition of soap decreases the surface tension of water , as we know the energy of spraying is directly proportional to the surface tension .

Under Graduate Entrance Exams NEET Entrance Exam # Physics Kinetic Theory Prepare / Learn

Q3. Anvils made of single crystals of diamond, with the shape as shown in Figure, are used to investigate behaviour of materials under very high pressures. Flat faces at the narrow end of the anvil have a diameter of 0.50 mm, and the wide ends are subjected to a compression force of 50,000 N. What is the pressure at the tip of the anvil?

A. 2.9

\times

1 0^{11}

B. 3.2

\times

1 0^{11}

C. 2.5

\times

1 0^{11}

D. 2.1

\times

1 0^{11}

Answer : Option C
Explaination / Solution:
No Explaination.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Ray Optics and Optical Instruments Prepare / Learn

Q4. A plano-convex lens is made of glass of refractive index 1.5.The focal length ƒ of the lens and radius of curvature R of its curved face are related as

A. ƒ = 2 R

B. ƒ = R /2

C. ƒ = 3 /2 R

D. ƒ = R

Answer : Option A
Explaination / Solution:
No Explaination.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Nuclei Prepare / Learn

Q5. In a nuclear reaction which of the following is conserved

A. Momentum only

B. Charge only

C. Sum of mass and energy only

D. All the above

Answer : Option D
Explaination / Solution:
No Explaination.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Thermal Properties of Matter Prepare / Learn

Q6.

A brass boiler has a base area of 0.15 m2 and thickness 1.0 cm. It boils water at the rate of 6.0 kg/min when placed on a gas stove. Estimate the temperature of the part of the flame in contact with the boiler. Thermal conductivity of brass = 109 J $s^{- 1} m^{- 1} K^{- 1}$ ; Heat of vaporization of water = 2256 $\times$ $1 0^{3} J k g^{- 1}$

A. 237

^{\circ}

B. 239

^{\circ}

C. 240

^{\circ}

D. 238

^{\circ}

Answer : Option D
Explaination / Solution:

Base area of the boiler, A = 0.15 m2
Thickness of the boiler, l = 1.0 cm = 0.01 m
Boiling rate of water, R = 6.0 kg/min
Mass, m = 6 kg
Time, t = 1 min = 60 s
Thermal conductivity of brass, K = 109 J s –1 m–1 K–1
Heat of vaporisation, L = 2256 × 103 J kg–1
The amount of heat flowing into water through the brass base of the boiler is

$Q = \frac{K A (T_{1} - T_{2})}{l} t$ ..........(1)

where,
T1 = Temperature of the flame in contact with the boiler
T2 = Boiling point of water = 100°C
Heat required for boiling the water

Q = mL ....… (ii)
Equating equations (i) and (ii), we get:
∴ mL = KA(T1 - T2) t / l
T1 - T2 = mLl / KAt
= 6 × 2256 × 103 × 0.01 / (109 × 0.15 × 60)
= 137.98 o C
Therefore, the temperature of the part of the flame in contact with the boiler is 237.98°C.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Units and Measurements Prepare / Learn

Q7. The length, breadth and thickness of a rectangular sheet of metal are 4.234 m, 1.005 m, and 2.01 cm respectively. Give the area of the sheet to correct significant figures.

8.72

m^{2}

m^{2}

B. 8.7221

m^{2}

C. 8.8

m^{2}

8.722

m^{2}

m^{2}

Answer : Option A
Explaination / Solution:

length, l = 4.234 m

breadth,b = 1.005 m

thickness, t = 2.01 cm = 2.01 × 10-2 m Area of the sheet = 2 (l × b + b × t + t × l) = 2 (4.234 × 1.005 + 1.005 × 0.0201 + 0.0201 × 4.234) = 2 (4.3604739) = 8.7209478 m2

As area can contain a maximum of three significant digits, therefore, rounding off, we get Area = 8.72 m2

Under Graduate Entrance Exams NEET Entrance Exam # Physics Alternating Current Prepare / Learn

Q8. In an L-R-C series circuit, the rms voltage across the resistor is 30.0 V, across the capacitor it is 90.0 V, and across the inductor it is 50.0 V. Rms voltage of the source is

A. 50.0 V

B. 60.0 V

C. 65.0 V

D. 55.0 V

Answer : Option A
Explaination / Solution:

VR=30V

VC=90V

VL=50V

V=(VC−VL)2+VR2−−−−−−−−−−−−−−√=(90−50)2+302−−−−−−−−−−−−−√=402+302−−−−−−−−√V=50volt

Under Graduate Entrance Exams NEET Entrance Exam # Physics Oscillations Prepare / Learn

Q9. Whose motion is an ideal case of SHM?

A. A simple pendulum with very small angle of swing

B. An electric dipole placed stably in a uniform electric field and then given a very small regular displacement

C. Shadow of a point mass having uniform circular motion, on the vertical diameter

D. None of these

Answer : Option D
Explaination / Solution:
No Explaination.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Magnetism and Matter Prepare / Learn

Q10. A bar magnet of magnetic moment 1.5 J/T lies aligned with the direction of a uniform magnetic field of 0.22 T. What is the amount of work required by an external torque to turn the magnet so as to align its magnetic moment normal to the field direction?

A. 0.33J

B. 0.23J

C. 0.38J

D. 0.43J

Answer : Option A
Explaination / Solution:
No Explaination.

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Under Graduate Entrance Exams NEET Entrance Exam Physics TEST : 129