Consider the following statements:
A. Surface tension arises due to extra energy of the molecules at the interior as compared to the molecules at the surface of a liquid.
B. As the temperature of a liquid rises, the coefficient of viscosity increases.
C. As the temperature of a gas increases, the coefficient of viscosity increases.
D. The onset of turbulence is determined by Reynolds number.
E. In a steady flow two streamlines never intersect.
Choose the correct answer from the options given below:
Answer: (A) C, D, E only
- A: It is the **surface** molecules that have extra energy (fewer neighbours pulling on them). Wrong.
- B: Liquid viscosity **decreases** as temperature rises. Wrong.
- C: Gas viscosity increases with temperature (faster molecules transfer more momentum between layers). Correct.
- D: Flow becomes turbulent when the Reynolds number exceeds a critical value. Correct.
- E: If two streamlines crossed, a fluid particle at that point would have two velocities at once. Correct.
C, D, E only.
Solution by Sreeraj P, M.Sc Physics