A body falling through a fluid reaches terminal velocity when
Correct answer: B. the upward drag and upthrust together balance the weight, so the net force is zero
- A. the drag force becomes zero
- B. the upward drag and upthrust together balance the weight, so the net force is zero
- C. the body stops moving completely
- D. gravity stops acting on the body
Explanation
Drag increases with speed, so the body accelerates until the retarding forces grow to match its weight, after which the acceleration is zero and the speed stays constant. The body is still moving, and gravity still acts; what has vanished is the resultant force, not any individual one. This is why a raindrop reaches the ground at a survivable speed rather than accelerating for its whole fall.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? support@testustad.com
About Terminal Velocity
Terminal velocity is the constant speed reached when gravitational force is balanced by fluid resistance. The topic covers drag, buoyant force, the conditions for zero acceleration, and how viscosity, object size, shape and density affect the limiting speed, with a distinction between free fall before and after terminal velocity.
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 Terminal Velocity questions
The terminal velocity of a small sphere falling through a viscous liquid is proportional to
Two spheres of the same size but different densities fall through the same viscous liquid. The denser one has
A skydiver opens a parachute. The terminal velocity
When an object attains terminal velocity, its acceleration is: