Physics Test 110

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Physics Test 110

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Question 1
4 / -1

Orbital radius of a satellite S of earth is four times that of a communication satellite C. Period of revolution of S is :-

A
4 days

B
8 days

C
16 days

D
32 days

Solution
Question 2
4 / -1

Three identical solid spheres move down three inclines A, B and C–all of the same dimensions. A is without friction, the friction between B and a sphere is sufficient to cause rolling without slipping, the friction between C and a sphere causes rolling with slipping. The kinetic energies of A, B, C at the bottom of the inclines are E_A, E_B, E_C.

A
E_A = E_B = E_C

B
E_A = E_B > E_C

C
E_A > E_B > E_C

D
E_A > E_B = E_C

Solution

In sliding without friction and in rolling without slipping, no work is done against friction.

Hence, kinetic energy = loss in gravitational potential energy. In rolling with slipping, some energy is lost in doing work against friction and kinetic energy is less than the loss in potential energy.
Question 3
4 / -1

A rectangular film of liquid is extended from (4cm × 2cm) to (5cm × 4cm). If the work done is 3×10^–4J. the value of the surface tension of the liquid is :

A
8.0 Nm^–1

B
0.250 Nm^–1

C
0.125 Nm^–1

D
0.2 Nm^–1

Solution

W = T × 2(ΔA)_upper

⇒ 3 × 10^–4 = T × 2 [20 – 8] × 10^–4

T = 0.125 N/m
Question 4
4 / -1

A rifle bullet of mass 0.1 kg strikes and embeds itself in a block of mass 0.9 kg. The block rests on a horizontal frictionless table and is attached to a spring as shown in fig. The impact compresses the spring by 0.2m. If a force of 1N compresses the spring by 2cm, calculate initial velocity of bullet.

A
5 ms^–1

B
5√2 ms^–1

C
10 ms^–1

D
10√2 ms^–1

Solution
Question 5
4 / -1

An organ pipe closed at one end has fundamental frequency of 1500 Hz. The maximum number of overtones generated by this pipe which a normal person can hear is

A
14

B
13

C
6

D
9
Question 6
4 / -1

A racing car moving towards a cliff sounds its horn. The driver observes that the sound reflected from the cliff has a pitch one octave higher than the actual sound of the horn. If v is the velocity of sound, the velocity of the car will be :-

A
v / √2

B
v / 2

C
v / 3

D
v / 4
Question 7
4 / -1

A 2 kg copper block is heated to 500°C and then it is placed on a large block of ice at 0°C. If the specific heat capacity of copper is 400 J/kg/°C and latent heat of fusion of water is 3.5 × 10⁵ J/kg. The amount of ice that can melt is :

A
(7/8) kg

B
(7/5) kg

C
(8/7) kg

D
(5/7) kg

Solution

Let x kg of ice can melt.

Using law of calorimetry,

heat lost by copper = heat gained by ice

2 × 400 × (500 - 0) = x × 3.5 × 10⁵

or x =
Question 8
4 / -1

Two moles of helium gas are taken along the path ABCD (as shown in figure). The work done by the gas is

A

B

C

D

Solution

AB → P = constant

W_AB = nRΔT = 2 × R × (750 – 250)

⇒ 1000 R

W_BC = 0 (∵ V = constant)

CD → T = constant
Question 9
4 / -1

Certain quantity of water cools from 70°C to 60°C in the first 5 minutes and to 54°C in the next 5 minutes. The temperature of the surroundings is :-

A
45°C

B
20°C

C
42°C

D
10°C

Solution
Question 10
4 / -1

Cooling rate of a sphere of 600 K at external environment (200 K) is R. When the temperature of sphere is reduced to 400 K then cooling rate of the sphere becomes :

A

B

C

D
None

Solution