Inertial Reference Frame Locally

[adam.kumayl]

Why can we not CHOOSE a reference frame locally and treat everything inside of it as an inertial reference frame. For example in a classroom, the classroom is moving with the Earth and so is a ball rolling down the class. Because they are both equally moving due to the Earth's rotation, why can't we just ignore that? Simply treat that class room as a inertial reference frame For THIS REASON..

(I know we can treat it as an inertial reference frame because the acceleration of the Earth for that short time and distance is negligible, but that's another reason, i would like to know why my reasoning is wrong, such that if they weren't negligible we could still ignore them.)

Thank you!

 

[Vanadium 50]

How many legs does a horse have if you call a tail a leg?

Four. Calling a tail a leg doesn't make it one.

 

[Dale]

Why can we not CHOOSE a reference frame locally and treat everything inside of it as an inertial reference frame. For example in a classroom, the classroom is moving with the Earth and so is a ball rolling down the class. Because they are both equally moving due to the Earth's rotation, why can't we just ignore that? Simply treat that class room as a inertial reference frame For THIS REASON..

(I know we can treat it as an inertial reference frame because the acceleration of the Earth for that short time and distance is negligible, but that's another reason, i would like to know why my reasoning is wrong, such that if they weren't negligible we could still ignore them.)

Non-inertial frames have fictitious forces. If those forces are not negligible then you cannot ignore them.

 

[Khashishi]

Are you familiar with the Coriolis effect. If we treated the surface of the Earth as an inertial reference frame, we would have no way to explain why vortices rotate clockwise in the northern hemisphere and counterclockwise in the southern hemisphere.

 

[PJC01]

Your reasoning is incorrect because an inertial reference frame is defined as a frame of reference in which Newton's laws of motion hold true without the influence of any external forces. In your example, the classroom is still subject to the Earth's rotation, which is an external force. This external force would affect the motion of the ball, and therefore, the classroom cannot be considered an inertial reference frame.

Additionally, even if the classroom and the ball were moving at the same velocity due to the Earth's rotation, there could still be other external forces at play that would affect the motion of the ball, such as air resistance or friction from the floor. These forces would also prevent the classroom from being considered an inertial reference frame.

In order to have a truly inertial reference frame, all external forces must be negligible. This means that even if the Earth's rotation is the main force at play, it must still be considered and accounted for in the frame of reference.