21.

70 calories of heat are required to raise the temperature of 2 moles of an ideal gas at constant pressure from 30°C to 35°C.  The amount of heat required to raise the temperature of the same sample of the gas increases with through the same range at constant volume is (Gas constant= 1·99 cal/K-mole)

• 30 cal

• 50 cal

• 70 cal

• 90 cal

3 mole of hydrogen is mixed with 1 mole of neon. The molar specific heat at constant pressure is

• $\frac{9 \mathrm{R}}{4}$

• $\frac{9 \mathrm{R}}{2}$

• $\frac{13 \mathrm{R}}{4}$

• $\frac{13 \mathrm{R}}{2}$

A bottle weighing 220 g and of area of cross-section 50 cm², and height 4 cm oscillates on the surface of water in vertical position. Its frequency of oscillation is

• 1.5 Hz

• 2.5 Hz

• 3.5 Hz

• 4.5 Hz

The time period of a particle undergoing SHM is 16 s. It starts motion from the mean position. After 2 s, its velocity is 0.4 m s^-1 .The amplitude is

• 1.44 m

• 0.72 m

• 2.88 m

• 0.36 m

A 5.5 metre length of string has a mass of 0.035 kg. If the tension in the string is 77 N, the velocity of the wave on the string is

• 210 m s^-1

• 40 m s^-1

• 110 m s^-1

• 55 m s^-1

Assertion:  Current is passed through a metallic wire so that it becomes red hot. When cold water is poured on half of its portion, the rest of the half portion becomes more hot. 

Reason:  Resistance decreases due to decrease in temperature.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: When height of a tube is less than liquid rise in the capillary tube, the liquid does not overflow. 

Reason: Product of radius of meniscus and height of liquid in the capillary tube always remain constant.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• f both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion:  The periodic time of a hard spring is less as compared to that of a soft spring. 

Reason:  The periodic time depends upon the spring constant, which is large for hard spring.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: It is not possible for a system, unaided by an external agency to transfer heat from a body at lower temperature to another body at a higher temperature.

Reason: It is not possible to violate the second law of thermodynamics

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: To hear distinct beats, difference in frequencies of two sources should be less than 10. 

Reason: More the number of beats per sec
more difficult to hear them.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.