An in-compressible fluid flows steadily through a horizontal cylindrical pipe. The pipe has radius '$3R$' at point A and '$1.5R$' at point B, further along the flow direction at the same level. If the velocity at point A is '$v$', then that at point B is

When $170$ J of energy is incident on a surface of a body, $17$ J of energy is reflected by it. If the coefficient of absorption is $0.7$, then the amount of energy transmitted will be

A black body is at temperature $827^\circ\text{C}$. The rate at which it emits energy is proportional to

If the two temperatures on Fahrenheit scale differ by $54^\circ\text{F}$, then the difference in temperature on the Celsius scale is