Free Fluid Dynamics MCQs with Answers
363 Fluid Dynamics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Fluid flow is described through speed, pressure and density, including steady flow and the equation of continuity for conserving mass. Bernoulli's equation relates pressure, speed and height, while fluid drag and terminal velocity explain why a falling object eventually moves at constant speed when drag balances its weight.
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Read the Fluid Dynamics notesFree MDCAT chapter notes with key terms363 questions · page 16 of 19
- A. Size of hole
- B. Height
- C. Acceleration
- D. None
Explanation: According to Torricelli's theorem, the velocity of efflux, v, through a hole in the side of a container is given by the formula v =…
Correct answer: Size of hole- A. Spot the same point
- B. A spot farther than B spot
- C. B Spot farther than A spot
- D. None
Explanation: Water coming out of hole A (at 3 m height) has greater efflux speed because the water column above it is deeper (7 m).
Correct answer: A spot farther than B spot- A. V/2
- B. V/16
- C. V
- D. V/4
Explanation: According to Poiseuille's Law, the flow rate (V) in a cylindrical tube is directly proportional to the fourth power of the radius of the…
Correct answer: V/4- A. 8
- B. 4
- C. 2
- D. 16
Explanation: The terminal velocity of a droplet is given by the relation Vt ∝ r2. When n droplets of radius 2mm coalesce into a single droplet, the…
Correct answer: 8305. There is a hole in a tank. of. water at the bottom. If pressure is. 3atm at bottom speed of efflux
- A. 20 m/s
- B. 20√2 m/s
- C. 10√2 m/s
- D. None
Explanation: To find the speed of efflux, we use Torricelli's theorem: v = √(2gh + 2P/ρ).
Correct answer: 20 m/s- A. V
- B. V2
- C. 1/V2
- D. V4
Explanation: The correct answer is V2. In fluid dynamics, when a fluid exits a tube with a certain velocity, the reaction force on the tube is…
Correct answer: V2- A. 8 cm
- B. 4 cm
- C. 3 cm
- D. 16 cm
Explanation: To solve this problem, we apply Torricelli's theorem, which gives the velocity of fluid efflux as \( v = \sqrt{2gh} \), where \( h \) is…
Correct answer: 8 cm- A. Energy is liberated
- B. Energy is absorbed
- C. Neither liberated nor absorbed
- D. Some mass is converted into energy
Explanation: When two droplets merge, the resulting larger droplet has a smaller total surface area compared to the sum of the surfaces of the two…
Correct answer: Energy is liberated- A. Density increases
- B. Density decreases
- C. Temperature increases
- D. Temperature decreases
Explanation: When 106 small drops coalesce to form a larger drop, the total surface area decreases.
Correct answer: Temperature increases- A. The soap film consists of two surface layers of molecules back to back
- B. The bubble encloses air inside it
- C. The pressure of air inside the bubble is less than the atmospheric pressure; that is why the atmospheric pressure has compressed it equally from all sides to give it a spherical shape
- D. Because of the elastic property of the film, it will tend to shrink to as small a surface area as possible for the volume it has enclosed
Explanation: The correct answer is Option C. In a soap bubble, the pressure inside the bubble is higher than the atmospheric pressure due to the…
Correct answer: The pressure of air inside the bubble is less than the atmospheric pressure; that is why the atmospheric pressure has compressed it equally from all sides to give it a spherical shape- A. ρ = (ρ1 + ρ2) / 2
- B. ρ = (ρ1 + ρ2) / (2ρ1ρ2)
- C. ρ = 2ρ1ρ2 / (ρ1 + ρ2)
- D. ρ = ρ1ρ2 / (ρ1 + ρ2)
Explanation: When two liquids of equal masses are mixed, the density of the mixture can be determined by considering the conservation of mass.
Correct answer: ρ = 2ρ1ρ2 / (ρ1 + ρ2)- A. ρ= ρ1+ρ2/2
- B. ρ= ρ1+ρ2/2ρ1ρ2
- C. ρ= 2ρ1ρ2/ρ1+ρ2
- D. ρ= ρ1ρ2/ρ1+ρ2
Explanation: If two liquids have equal volumes, then the density of the mixture is simply the harmonic mean of the two densities:𝜌 mix=Total mass/…
Correct answer: ρ= 2ρ1ρ2/ρ1+ρ2- A. t
- B. 4t
- C. 2t
- D. t/4
Explanation: According to Torricelli's theorem, the velocity of efflux of a fluid under gravity through a small hole at the bottom of a container is…
Correct answer: 2t- A. 4:9
- B. 9:4
- C. 8:27
- D. 1:1
Explanation: To solve this problem, we apply the principle of continuity, which states that the product of the cross-sectional area and velocity of…
Correct answer: 4:9- A. 4:49
- B. 49:4
- C. 2:7
- D. 7:2
Explanation: The critical velocity (Vc) can be calculated using the formula: Vc ∝ (η/ρ), where η is the coefficient of viscosity and ρ is the density…
Correct answer: 4:49- A. Velocity more than the critical velocity
- B. Velocity less than the critical velocity
- C. Irregular flow
- D. Molecules crossing from one layer to another
Explanation: The correct answer is Option B: Velocity less than the critical velocity.
Correct answer: Velocity less than the critical velocity- A. v
- B. √v
- C. 1/√v
- D. v2
Explanation: The correct answer is v. According to Stokes' Law, the viscous drag force experienced by a small spherical object moving slowly through a…
Correct answer: v- A. 4.9 m/s
- B. 9.8 m/s
- C. 4.42 m/s
- D. 3.75 m/s
Explanation: To find the speed of efflux of water from a hole in the tank, we use Torricelli's Theorem, which states: v = √(2gh), where v is the speed…
Correct answer: 4.42 m/s- A. Before hail
- B. After hail
- C. At the same time
- D. None of the above
Explanation: When objects of the same size fall through the air, the effects of air resistance and material density become significant.
Correct answer: After hail- A. 1/2
- B. 1
- C. 3/2
- D. 2
Explanation: The correct answer is 1/2. Using dimensional analysis, the speed v (dimension [L][T]^-1) must be proportional to the square root of the…
Correct answer: 1/2