Physics Test

Question 1
3 / -1

A luminous point object is moving along the principal axis of a concave mirror of focal length 12 cm towards it. When its distance from the mirror is 20 cm its velocity is 4 cm/s . The velocity of the image in cm/s at that instant

A
6cm/s, towards the mirror

B
6cm/s, away from the mirror

C
9cm/s, away from the mirror

D
9cm/s, towards the mirror

Question 2
3 / -1

Directions: The following question has four choices, out of which ONE or MORE can be correct.

Two blocks A and B, each of mass m, are connected by a massless spring of natural length L and spring constant k. The blocks are initially resting on a smooth horizontal floor with the spring at its natural length, as shown in the figure. A third identical block C, also of mass m, moves on the floor with a speed v along the line joining A and B, and collides elastically with A. Then,

A
the kinetic energy of the A-B system, at maximum compression of the spring, is zero

B
the kinetic energy of the A-B system, at maximum compression of the spring, is mv²/4

C
the maximum compression of the spring is v √(m/k)

D
None of the above

Question 3
3 / -1

Two blocks P and Q are connected by a light inextensible string passing over a smooth pulley fixed as shown in the Figure. The coefficient of friction of blocks P and Q to the table is μ = 0.3; the mass of the block Q is 20 kg. The mass of the block P for the block just to slip is

A
48.6 kg

B
50.6 kg

C
52.4 kg

D
54.8 kg

Question 4
3 / -1

A monochromatic light source of wavelength $λ$ is placed at S. Three slits $S_{1}, S_{2}$ and $S_{3}$ are equidistance from the source $S$ and the point $P$ on the screen. $S_{1} P - S_{2} P = λ / 6$ and $S_{1} P - S_{3} P = 2 λ / 3$ . If I be the intensity at $P$ when only one slit is open, the intensity at $P$ when all the three slits are open is?

A
3I

B
5I

C
8I

D
zero

Question 5
3 / -1

Directions: The following question has four choices, out of which ONE or MORE can be correct.

The coordinates of a particle moving in a plane are given by:

x(t) = a cos (pt) and y(t) = b sin (pt), where a, b (< a) and p are positive constants of appropriate dimensions.

Which of the following statements is/are correct?

A
The path of the particle is an ellipse.

B
The velocity and acceleration of the particle are normal to each other at (t = π/2p).

C
The acceleration of the particle is always directed towards a focus.

D
All are correct

Question 6
3 / -1

If $E, M, J$ and $G$ denote energy, mass, angular momentum and gravitational constant respectively. Then the dimensions of $\frac{E J^{2}}{M^{5} G^{2}}$ are same as that of:

A
Length

B
Mass

C
Angle

D
Time

Question 7
3 / -1

An ammeter is designed by shunting a 60 Ω galvanometer with a 60 Ω resistance. The additional shunt that should be connected across it to double the range is

A
20 Ω

B
25 Ω

C
30 Ω

D
35 Ω

Question 8
3 / -1

Directions: The following question has four choices, out of which ONE or MORE can be correct.

A particle of mass m moves on the x-axis as follows:

It starts from rest at t = 0 from the point x = 0, and comes to rest at t = 1 at the point x = 1. No other information is available about its motion at intermediate times (0 < t < 1). If α denotes the instantaneous acceleration of the particle, then

A
α cannot remain positive for all t in the interval 0 ≤ t ≤ 1

B
|α| cannot exceed 2 at any point in its path

C
α must change sign during the motion, but no other assertion can be made with the information given

D
None of these

Question 9
3 / -1

A circular conducting loop of radius R carries a current I. Another straight infinite conductor carrying current I passes through the diameter of this loop as shown in the figure. The magnitude of force exerted by the straight conductor on the loop is :-

A
πμ0i²

B
μ₀i²

C
(μ₀i²)/2π

D
(μ₀i²)/π

Question 10
3 / -1

Directions: The following question has four choices, out of which ONE or MORE can be correct. A simple pendulum of length $L$ and mass (bob) $M$ is oscillating in a plane about a vertical line between angular limits $- ϕ$ and $+ ϕ$ . For an angular displacement $θ (| θ | < ϕ)$ , the tension in the string and the velocity of the bob are $T$ and $v$ , respectively. The relation(s) that hold(s) good under the above conditions is/are:

A
T cosθ = Mg

B
T = Mg cosθ

C
The magnitude of the tangential acceleration of the bob |aT| = g sinθ

D
None of these

Question 11
3 / -1

Directions: The following question has four choices, out of which ONE or MORE can be correct.

A uniform bar of length 6a and mass 8m lies on a smooth horizontal table. Two point masses m and 2m moving in the same horizontal plane with speed 2 v and v, respectively, strike the bar [as shown in the figure] and stick to the bar after collision. Denoting angular velocity (about the centre of mass), total energy and centre of mass velocity respectively by ω , E and vc, we have after collision:

A
v_c = 0

B
ω = v/5a

C
E = 3/5 mv²

D
All of the above

Question 12
3 / -1

One million small identical drops of water, all charged to the same potential, are combined to form a single large drop. If E is the sum of the electrostatic energy of each small drop, the combined energy of the large drop is

A
10^–4 E

B
E

C
10⁶ E

D
10⁴ E

Question 13
3 / -1

Consider telecommunication through optical fibres. Which of the following statements is NOT true?

A
Optical fibres can be of graded refractive index

B
Optical fibres are subjected to electromagnetic interference from outside

C
Optical fibres have extremely low transmission loss

D
Optical fibres may have homogeneous core with a suitable cladding

Question 14
3 / -1

The number of AM broadcast stations that can be accommodated at a 150 kHz band width, if the highest frequency modulating carrier is 5 kHz is

A
15

B
18

C
21

D
24

Question 15
3 / -1

A square lead slab of side a = 50 cm and thickness t = 0.5 cm is subjected to a shearing force of magnitude F = 9 × 10⁴ N. If the shear modulus of lead is η = 5.6 × 10⁹ Pa, then how much work is done by the force?

A
5.4 × 10^–3 J

B
6 × 10^–3 J

C
4.5 × 10^–2 J

D
1.44 × 10^–2 J

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Physics Test - ...

Question 1

6cm/s, towards the mirror

6cm/s, away from the mirror

9cm/s, away from the mirror

9cm/s, towards the mirror

Question 2

the kinetic energy of the A-B system, at maximum compression of the spring, is zero

the kinetic energy of the A-B system, at maximum compression of the spring, is mv2/4

the maximum compression of the spring is v √(m/k)

None of the above

Question 3

48.6 kg

50.6 kg

52.4 kg

54.8 kg

Question 4

3I

5I

8I

zero

Question 5

The path of the particle is an ellipse.

The velocity and acceleration of the particle are normal to each other at (t = π/2p).

The acceleration of the particle is always directed towards a focus.

All are correct

Question 6

Length

Mass

Angle

Time

Question 7

20 Ω

25 Ω

30 Ω

35 Ω

Question 8

α cannot remain positive for all t in the interval 0 ≤ t ≤ 1

|α| cannot exceed 2 at any point in its path

α must change sign during the motion, but no other assertion can be made with the information given

None of these

Question 9

πμ0i2

μ0i2

(μ0i2)/2π

(μ0i2)/π

Question 10

T cosθ = Mg

T = Mg cosθ

The magnitude of the tangential acceleration of the bob |aT| = g sinθ

None of these

Question 11

vc = 0

ω = v/5a

E = 3/5 mv2

All of the above

Question 12

10–4 E

E

106 E

104 E

Question 13

Optical fibres can be of graded refractive index

Optical fibres are subjected to electromagnetic interference from outside

Optical fibres have extremely low transmission loss

Optical fibres may have homogeneous core with a suitable cladding

Question 14

15

18

21

24

Question 15

5.4 × 10–3 J

6 × 10–3 J

4.5 × 10–2 J

1.44 × 10–2 J

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Question Analysis

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the kinetic energy of the A-B system, at maximum compression of the spring, is mv²/4

πμ0i²

μ₀i²

(μ₀i²)/2π

(μ₀i²)/π

v_c = 0

E = 3/5 mv²

10^–4 E

10⁶ E

10⁴ E

5.4 × 10^–3 J

6 × 10^–3 J

4.5 × 10^–2 J

1.44 × 10^–2 J