Physics Test 152

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Physics Test 152

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Weekly Quiz Competition

Question 1
4 / -1

200 MeV of energy may be obtained per fission of U²³⁵. A reactor is generating 1000 kW of power. The rate of nuclear fission in the reactor is :-

A
1000

B
2 × 10⁸

C
3.125 × 10¹⁶

D
931

Solution

Power = 1000 kW = 10⁶ J/s
Rate of nuclear fission =

= 3.125 × 10¹⁶
Question 2
4 / -1

In an α-decay kinetic energy of α particle is 98 MeV and Q-value of the reaction is 100 MeV. The mass number of the mother nucleus is. (Assume that daughter nucleus is in ground state):-

A
100

B
200

C
300

D
None of these

Solution
Question 3
4 / -1

The electric potential between a proton and an electron is given by where r₀ is a constant. Assuming Bohr's model to be applicable, write variation of r_n with n, n being the principal quantum number :-

A
r_n∝ n

B
r_n∝ 1/n

C
r_n∝ 1/n²

D
r_n∝ n²

Solution
Question 4
4 / -1

10 gm of ice at –5°C is added to 10 gm of water at 60°C. Specific heat of water = 1 cal/gm-°C; specific heat of ice = 0.5 cal/gm-°C and latent heat of ice = 80 cal/gm. The resulting temperature of the mixture is :-

A
0°C

B
2°C

C
–2°C

D
10°C

Solution

Let us first decide whether whole of the ice melts or not. The question is solved in steps as follows:

(i) Heat supplied by 10 gm of water in cooling from 60°C to 0°C = mS.Δt

= 10 × 1 × (60 – 0) = 600 cal

(ii) Heat required to raise the temperature of 10 gm ice from –5°C to 0°C

= 10 × 0.5 × (0 – (–5)) = 25 cal

(iii) Heat required to melt 10 gm ice at 0°C into water at 0°C = mL = 10 × 80 = 800 cal

Now the heat required to melt the ice completely,

= (a) + (b) = 25 + 800 = 825 cal

Since heat supplied by the water to lower its temperature to 0°C is only 600 cal, therefore whole of the ice does not melt. The resulting temperature of the mixture is thus 0°C.
Question 5
4 / -1

28 gm of N₂ gas is contained in a flask at a pressure of 10 atm and at a temperature of 57°C. It is found that due to leakage in the flask, the pressure is reduced to half and the temperature reduced to 27°C. The quantity of N₂ gas that leaked out is

A
11/20 gm

B
20/11 gm

C
5/63 gm

D
63/5 gm

Solution
Question 6
4 / -1

The average translational energy and the rms speed of molecules of a sample of oxygen gas at 300 K are 6.21 × 10^–21 J and 484 m/s respectively. The corresponding values at 600 K are nearly (assuming ideal gas behaviour) :

A
12.42 × 10^–21 J ; 968 m/s

B
8.78 × 10^–21 J ; 684 m/s

C
6.21 × 10^–21 J ; 968 m/s

D
12.42 × 10^–21 J ; 684 m/s

Solution
Question 7
4 / -1

Directions For Questions

Fig. shows the displacement of a particle moving along x-axis as a function of time. The acceleration of the particle is zero in the region :

(a) AB (b) BC (c) CD (d) DE

...view full instructions

Select correct alternative

A
a, b

B
a, c

C
b, d

D
c, d

Solution

Slope of s-t curve is equal to velocity.

When slope of s-t curve is constant, acceleration must be zero. So it is in the part AB and CD.
Question 8
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 9
4 / -1

A balloon of mass M is descending with a constant acceleration g/3. When a mass m is released from the balloon it starts rising with the same acceleration g/3. The value of m is (Assuming that its volume does not change) :-

A
M/2

B
M/4

C
4M

D
2M

Solution
Question 10
4 / -1

A body is sliding down an inclined plane (angle of inclination 45°). If the coefficient of friction is 0.5 and g = 9.8 m/s². then the downward acceleration of the body in m/s² is :-

A

B
4.9 √2

C
19.6 √2

D
4.9

Solution