Consider a single particle of a fluid in a test tube. The test tube is placed in
ID: 2060326 • Letter: C
Question
Consider a single particle of a fluid in a test tube. The test tube is placed in a centrifuge and spun up to a very high speed. As the tube spins, the particle drifts toward the back of the test tube (away from the center of the centrifuge). Eventually, the particle comes to stop and remains at rest with respect to the test tube. An observer sitting on the test tube (and spinning with it) claims that there are two forces in balance on the particle: a force due to pressure in the fluid and the centrifugal force. Since the centrifugal force does not exist in an inertial frame of reference, what force does an inertial observer in the lab say is balancing the force due to the pressure of the fluid?(a) The normal force
(b) The force of gravitational attraction with the Earth
(c) The centripetal force
(d) None; the forces are not balanced.
Explanation / Answer
A) normal force
The fluid exerts a pressure down, and the normal force balances it back up.
Rating appreciated!