Physics Test 248

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Physics Test 248

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Question 1
4 / -1

A rod PQ of mass M and length L is hinged at end P. The rod is kept horizontal by a massless string tied to point Q as shown in the figure. When the string is cut, the initial angular acceleration of the rod is:

A
g / L

B
2g / L

C
2g / 3L

D
3g / 2L

Solution
Question 2
4 / -1

A particle is projected with a velocity v, so that its range on a horizontal plane is twice the greatest height attained. If g is acceleration due to gravity, then its range is

A
4v²/5g

B
4g/5v²

C
4v³/5g²

D
4v/5g²

Solution
Question 3
4 / -1

A body starts from rest, the ratio of distances travelled by the body during 3^rd and 4^thseconds is :

A
7/5

B
5/7

C
7/3

D
3/7

Solution

The velocity after 2 sec = 2a and velocity after 3 sec = 3a

For some constant acceleration a,

Now distance travelled in third second, s₃ = 2a + 1 / 2 a

= 5/2 a

Similarly distance travelled in fourth second, s₄= 3a + 1 / 2 a

= 7/2 a

Hence the required ratio is 5/7
Question 4
4 / -1

A ray of light is incident at an angle of 60° on one face of a prism of angle 30°. The emergent ray of light makes an angle of 30° with incident ray. The angle made by the emergent ray with second face of prism will be:

A
0°

B
90°

C
30°

D
45°

Solution

For the prism, angle of deviation is given by:

Hence, emergent ray will be perpendicular to the second face or we say that the angle made by the emergent ray is 90°.
Question 5
4 / -1

The diagram of a logic circuit is given below. The output F of the circuit is given by:

A
W. (X + Y)

B
W. (X. Y)

C
W + (X. Y)

D
W + (X + Y)

Solution

By law of distribution of Boolean Algebra, we have A+ (B. C) = (A+B). (A + C)

Step 1: Write outputs for the OR gates with inputs W and X, and W and Y.

Input for first OR gate are W and X. The output for this OR gate is, Y₁ = W + X

Input for second OR gate are W and Y. The output for this OR gate is, Y₂ = W + Y

Step 2: Write output for AND gate whose inputs are the output of OR gate.

F = Y₁ • Y₂⇒ F = (W + X). (W + Y)

By using Law of distribution of Boolean Algebra, A + (B. C) = (A+B). (A + C)

Therefore, F = W + (X. Y)
Question 6
4 / -1

In the circuit shown in the Figure, cell is ideal and R₂ = 100Ω. A voltmeter of internal resistance 200Ω reads V₁₂ = 4 V and V₂₃ = 6 V between the pair of points 1 - 2 and 2 - 3 respectively. What will be the reading of the voltmeter between the points 1 - 3.

A
19 V

B
12 V

C
15 V

D
13 V

Solution
Question 7
4 / -1

The energy required to separate the typical middle mass nucleus into its constituent nucleons is:

(Mass of 119.902199amu, mass of proton = 1.007825amu and mass of neutron = 1.008665amu)

A
921 MeV

B
821 MeV

C
1021 MeV

D
1121 MeV

Solution

Given, Z = 50, A - Z = 120 - 50 = 70

Δm = Z.m_p + (A - Z) m_n - M= [50 × 1.007825 +70 × 1.008665 - 119.902199] = 1.095601 MeV

E = 1.095601 × 931.478 MeV = 1020.53 MeV ≈ 1021 MeV
Question 8
4 / -1

The astronomical phenomenon when the planet Venus passes directly between the Sun and the earth is known as Venus transit. For two separate persons standing on the earth at points M and N, the Venus appears as black dots at points M' and N' on the Sun. The orbital period of Venus is close to 220 days. Assuming that both earth and Venus revolve on circular paths and taking distance MN = 1000 km, calculate the distance M'N' on the surface of the Sun. [Take (2.75)^1/3 = 1.4]

A
2500 km

B
2000 km

C
3500 km

D
1500 km

Solution

Let radius of circular orbit of the Earth and Venus be r_e and r_v respectively (r_c/r_v) = (365/220)² [Kepler's third law]

⇒ r_c/r_v = (2.75)^1/3 = 1.4

From the drawing given in the problem M'N'/MN = N'V/NV
Question 9
4 / -1

A straight wire of length L and radius a has a current I. A particle of mass m and charge q approaches the wire moving at a velocity v in a direction anti parallel to the current. The line of motion of the particle is at a distance r from the axis of the wire. Assume that r is slightly larger than a so that the magnetic field seen by the particle is similar to that caused by a long wire. Neglect end effects and assume that speed of the particle is high so that it crosses the wire quickly and suffers a small deflection θ in its path. Calculate θ.

A

B

C

D

Solution

This force is always perpendicular to the velocity. Since deflection is small, the force is nearly in (↑) direction always.
Question 10
4 / -1

Two hollow-core solenoids, A and B, are connected by a wire and separated by a large distance, as shown in the diagram. Two bar magnets, 1 and 2, are suspended just above the solenoids. If the magnet 1 is dropped through solenoid A as shown, then the magnet 2 will simultaneously be

A
Attracted by a magnetic force towards solenoid B

B
Repelled by a magnetic force away from solenoid B

C
Unaffected by solenoid B

D
Repelled by an electric force away from solenoid B

Solution

As the magnet -1 falls into solenoid A, the magnetic flux associated with solenoid A increase. From Lenz's law induced current in solenoid A will oppose this increase in magnetic flux. Hence direction of induced current in solenoids is as shown. The nature of magnetic field produced by solenoid B is as shown. Therefore magnet 2 will be attracted by magnetic field due to solenoid B.