# Rotation relative to an inertial frame

• johnny_bohnny
In summary, the Earth has a tangential velocity of approximately 0.5 km/s at the equator due to its rotation. When combined with inertial motion, these velocities add vectorially, resulting in a different value at each point on Earth.
johnny_bohnny
Earth has a huge angular velocity regarding its rotation. Now let's imagine that the Earth has the velocity of 400 km/s relative to some inertial frame. What will be the velocity of Earth when we take the rotation into account combined with inertial motion? How do the 2 combine?

johnny_bohnny said:
Earth has a huge angular velocity regarding its rotation.
I think that you mean "huge tangential velocity". The angular velocity is not huge, it is 0.00007 1/s. The tangential velocity is about 0.5 km/s at the equator, which may or may not be "huge" depending on the context.

johnny_bohnny said:
What will be the velocity of Earth when we take the rotation into account combined with inertial motion? How do the 2 combine?
Velocities add vectorially. Don't forget that the tangential velocity is pointing in a different direction at each point on the earth, so you can do this addition for each point on the Earth and you will get a different value.

## 1. What is an inertial frame?

An inertial frame of reference is a coordinate system in which the laws of motion hold true without any external forces acting on the system. In other words, an object in an inertial frame will either remain at rest or maintain a constant velocity unless acted upon by an external force.

## 2. How is rotation relative to an inertial frame measured?

Rotation relative to an inertial frame is measured using angular velocity, which is the rate of change of angular displacement over time. It is typically measured in radians per second and can be calculated using the formula: ω = Δθ / Δt, where ω is the angular velocity, Δθ is the change in angular displacement, and Δt is the change in time.

## 3. How is rotation relative to an inertial frame different from rotation in a non-inertial frame?

In a non-inertial frame of reference, the laws of motion do not hold true due to the presence of external forces or accelerations. This means that the measurements of rotation in a non-inertial frame may differ from those in an inertial frame. In other words, an object may appear to be rotating in a non-inertial frame, even if it is not rotating in an inertial frame.

## 4. Can rotation relative to an inertial frame be affected by external forces?

No, rotation relative to an inertial frame is not affected by external forces. In an inertial frame, the laws of motion hold true, which means that an object will maintain a constant angular velocity unless acted upon by an external torque. However, the measurement of rotation may be affected if the external forces cause the frame to become non-inertial.

## 5. How is the Coriolis effect related to rotation relative to an inertial frame?

The Coriolis effect is a phenomenon that occurs due to the rotation of the Earth and its effect on moving objects. It is related to rotation relative to an inertial frame because the Earth can be considered an inertial frame, and the Coriolis effect is a result of the rotation of the Earth relative to objects on its surface. This effect is responsible for the rotation of hurricanes, the curvature of winds, and the trajectory of moving objects on Earth.

• Mechanics
Replies
1
Views
768
• Mechanics
Replies
3
Views
1K
• Mechanics
Replies
6
Views
1K
• Mechanics
Replies
12
Views
3K
• Mechanics
Replies
8
Views
2K
• Mechanics
Replies
15
Views
905
• Mechanics
Replies
25
Views
1K
• Mechanics
Replies
2
Views
741
• Mechanics
Replies
17
Views
2K
• Mechanics
Replies
2
Views
802