Physics Test 136

Result

Physics Test 136

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Weekly Quiz Competition

Question 1
4 / -1

In the figure shown the acceleration of A is, , then the acceleration of B is : (A remains in contact with B)

A

B

C

D

Solution
Question 2
4 / -1

The speed of sound in hydrogen gas at N.T.P. is 1,328 ms^-1. What will be its value in air at N.T.P., if density of hydrogen is 1/16th that of air?

A
340 ms^-1

B
332 ms^-1

C
320 ms^-1

D
293 ms^-1

Solution
Question 3
4 / -1

A balloon that is initially flat, is inflated by filling it from a tank of compressed air. The final volume of the balloon is 5m³. The barometer reads 95 kPa. The work done in this process is

A
4.75 J

B
4.75×10⁷J

C
4.75×10³ J

D
4.75×10⁵ J

Solution

W = P Δ V⁡ = 95 × 10³ × (5-0)
= 4.75 × 10⁵ J
Question 4
4 / -1

Two bodies of same mass tied with an inelastic string of length together on a horizontal surface. One a horizontal surface of them is projected vertically upwards with velocity ⁡Find the maximum height up to which the centre of mass of system of the two masses rises.

A
3I

B
l/2

C
3l/2

D
l

Solution

Velocity of B when string is just taut

After string in taut both will move up with same speed,

By this time centre of mass in at h = l/2
Question 5
4 / -1

The electric potential at a point (x, y, z) is given by V = -x²y - xz³ + 4 The electric field at that point is

A

B

C

D

Solution

The electric potential at a point,
Question 6
4 / -1

Binding energy per nucleon versus mass number curve for nuclei is shown in figure. W, X, Y and Z are four nuclei indicated on the curve. The process that would release energy is

A
Y → 2Z

B
W → X + Z

C
W → 2Y

D
X → Y + Z

Solution

Energy is released in a process when total binding energy of the nucleus (= binding energy per nucleon x number of nucleons) is increased or we can say, when total binding energy of products is more than the reactants.
Binding energy of reactants = 120 x 7. 5 = 900 MeV
and binding energy of products = 2 (60 x 8. 5)
= 1020 MeV > 900 MeV.
Question 7
4 / -1

A wire of length 1.0 m and radius 10^-3 m is carrying a heavy current and is assumed to radiate as a black body. At equilibrium, its temperature is 900 K while that of the surroundings is 300 K. The resistivity of the material of the wire at 300 K is π² × 10^-8 ohm-m and its temperature coefficient of resistance is 7.8× 10⁻³ C^o. Find the current in the wire. [Given Stefan's constant = 5.68 × 10^-8 W/m²K⁴]

A
18 A

B
36 A

C
54 A

D
72 A

Solution

According to Stefan's law power radiated by a black body is given by.

According to the given problem Equations (i) and (ii) represent the same.
Question 8
4 / -1

50 V battery is supplying a steady current of 10 amp when connected to an external resistor. If the efficiency of the battery at this current is 25%, then internal resistance of battery is:

A
2.5 Ω

B
1.25 Ω

C
5 Ω

D
3.75 Ω

Solution
Question 9
4 / -1

A capacitor of capacitance C is charged to a potential difference V from a cell and then disconnected from it. A charge +Q is now given to its positive plate. Now, the potential difference across the capacitor is.

A

B

C

D

Solution

Initially

After charge Q is given

Charge distribution is
Question 10
4 / -1

Energy from the sun falls on the earth at a rate of 1353 W/m², which is known as solar constant, i.e., the power incident per unit area per second at the top of atmosphere. Find the r.m.s values of the electric and magnetic fields in the sunlight reaching the top of the atmosphere.

A
714.0 V/m, 2.38 × 10^–6 T

B
7.14 V/m, 2.38 × 10^-8 T

C
71.4 V/m, 2.38 × 10^–7 T

D
None of these

Solution

For an electromagnetic wave of sinusoidal form