21.

Equation of a progressive sound wave is y = a sin $\left(400 \mathrm{\pi t} - \frac{\mathrm{\pi x}}{0.85}\right)$ where x in (metre), t (second), then frequency of wave is

• 200 Hz

• 400 Hz

• 500 Hz

• 600 Hz

Wavelength of the wave in the above question is

• 1.7 m

• 8.5 m

• 0.85 m

• 0.17 m

Relation of wavelengths of sound and light is

• λ_S < λ_L

• λ_S > λ_L

• λ_S = λ_L

• None of these

Dancing of small pieces of camphor on the surface of water is due to

• viscosity

• surface tension

• weight

• lifting force

Relation between specific heats of an ideal gas

• C_p + C_V = R

• C_p − C_V = R

• $\frac{{\mathrm{C}}_{\mathrm{p}}}{{\mathrm{C}}_{\mathrm{V}}} = \mathrm{R}$

• $\frac{{\mathrm{C}}_{\mathrm{V}}}{{\mathrm{C}}_{\mathrm{p}}} = \mathrm{R}$

Who gave the kinetic molecular theory of gas?

• Device

• Einstein

• Newton

• Bernoulli

Potential energy of a particle at a distance x from mean position, which is executing simple harmonic motion

• $\frac{1}{2} {\mathrm{m\omega }}^2{\mathrm{x}}^2$

• zero

• ${\mathrm{m}}^2\mathrm{\omega x}$

• $\frac{1}{2} {\mathrm{m}}^2{\mathrm{\omega }}^2{\mathrm{x}}^2$

Energy stored in the unit volume of a wire due to its elasticity is 

• $\frac{1}{2} (\mathrm{force} \times \mathrm{strain})$

• $\frac{1}{2} \mathrm{stress} \times \mathrm{strain}$

• stress/strain

• force/strain

Value of - 40°C in Fahrenheit scale is

• - 40F

• 32 F

• - 32 F

• 40°C

The amount of heat required to change 1 g (0°C) of ice into water of 100°C, is

• 716 cal

• 500 cal

• 180 cal

• 100 cal