A rain drop of radius 'r' fall in air with a terminal speed vt what is the terminal speed of radius 2r
Correct answer: C. 4Vt
- A. Vt√2
- B. Vt
- C. 4Vt
- D. 2Vt
Explanation
The terminal velocity of a raindrop is governed by the balance between gravitational force and drag force. For a spherical raindrop moving through air, the drag force is proportional to the square of its radius. When the radius is doubled, the terminal velocity is proportional to the square of the new radius, leading to an increase by a factor of 4 (since (2r)^2 = 4r^2). Therefore, the terminal speed becomes 4Vt. Option A incorrectly assumes a simple square root relationship, Option B ignores the change in radius, and Option D assumes a linear increase, all of which are incorrect.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? [email protected]
About Fluid Dynamics
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.
Practise Fluid Dynamics
363 free Fluid Dynamics MCQs from Physics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Physics questions like this
Physics is on 16 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
More Fluid Dynamics questions
The equation η+1/2ρv2+ρgh constant implies that
Bernoulli's equation relates which of the following quantities?
Bernoulli's equation is an accordance with?
Eight spherical rain drops of same mass and radius are falling down with a terminal velocity of 6cm/s if they collapse to form 1 big drop what will be its terminal speed? (neglect the buoyant force or buoyancy due to air)
According to equation of continuity when water falls its speed increases while its cross sectional area
Venturi relation is one of application of