How Does Angular Velocity Affect Instantaneous Acceleration in Rotating Systems?

In summary, the author is discussing the instantaneous acceleration of a projectile fired along a line of longitude on a rotating sphere, taking into account the angular velocity of the sphere and the projectile. They are also mentioning a "reactive Coriolis force" and explaining how it relates to the inertial Coriolis force. The author's explanation may be confusing and they are asking for clarification.
  • #1
WMDhamnekar
MHB
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Homework Statement:: Find the instantaneous acceleration of a projectile fired along a line of longitude (with angular velocity of ##\gamma##constant relative to the sphere) if the sphere
is rotating with angular velocity ##\omega##.
Relevant Equations:: None

Find the instantaneous acceleration of a projectile fired along a line of longitude (with angular velocity of ##\gamma## constant relative to the sphere) if the sphere is rotating with angular velocity ##\omega##. Using the following author's answer, I computed instantaneous acceleration of a projectile fired ##\ddot{r}= -\gamma^2 r + 2\omega \gamma r \cos{\gamma t } \hat{\ell} -\omega^2 r \sin{\gamma t}\hat{n}##
1655365753322.png

1655364969961.png

1655365024037.png

Now, what is the instantaneous acceleration in case of Rocket instead of Projectile?

I don't understand the author's explanation which is as follows:

1655365695497.png

1655365837624.png


Would anyone here explain me the exact meaning of author's explanation and above picture?[Moderator's note: moved from a homework forum.]
 
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  • #2
I disagree with the author's description.

The author is describing a "reactive Coriolis force" -- the real force required to resist the inertial Coriolis force which manifests in the rotating frame.

The Coriolis force is the eastward inertial force which would cause a deflection away from the rails.

This Coriolis force is an inertial force. It exists in the rotating frame only. In other frames, the same accelerating separation from the rails would still exist (were it not for the force from the rails). But that separation would be explained differently. For instance, in an inertial frame, we would have a straight line trajectory deviating from a curved and accelerating set of rails below it.

The "reactive Coriolis force" is the westward interaction force from the rails which keeps the object on the rails in spite of this.

Some adjectives for "real" forces: Interaction, real, physical, reactive
Some adjectives for "fictitious" forces: Inertial, fictitious, pseudo

"Interaction" and "inertial" are nice adjectives because they are descriptive and not pejorative.

Edit to add...

The adjective "reactive" is one that I've never seen applied to the Coriolis force. It is commonly used when talking about the centrifugal force. I use it here in a somewhat analogous way:

The inertial centrifugal force is the fictitious force that manifests in a rotating frame and explains the tendency of a ball on a string to fly away from the center.

The "reactive" centrifugal force is the real force from the ball on the string that holds the ball on its circular path in spite of its tendency to fly away.
 
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What is instantaneous acceleration?

Instantaneous acceleration is the rate of change of velocity at a specific moment in time. It is a measure of how quickly the velocity of an object is changing at a particular instant.

How is instantaneous acceleration calculated?

Instantaneous acceleration can be calculated by taking the derivative of the velocity with respect to time. This can be represented mathematically as a = dv/dt, where a is acceleration, v is velocity, and t is time.

What is the difference between instantaneous acceleration and average acceleration?

Average acceleration is the change in velocity over a specific period of time, while instantaneous acceleration is the change in velocity at a particular moment in time. Average acceleration gives an overall picture of the acceleration of an object, while instantaneous acceleration provides a more detailed view of how the velocity is changing at any given time.

How is instantaneous acceleration related to velocity and position?

Instantaneous acceleration is directly related to velocity and position. Velocity is the rate of change of position, and acceleration is the rate of change of velocity. Therefore, instantaneous acceleration is the second derivative of position with respect to time.

What factors can affect instantaneous acceleration?

The factors that can affect instantaneous acceleration include the mass of the object, the force acting on the object, and any external factors such as friction or air resistance. In addition, instantaneous acceleration can also be affected by changes in the direction of motion.

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