Understanding Inertia: Explaining the Door Closing Phenomenon in Moving Cars

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Discussion Overview

The discussion centers on understanding the phenomenon of a car door closing when the vehicle accelerates forward, specifically from the perspective of a ground frame of reference. Participants explore the forces acting on the door and the mechanics involved in its motion during acceleration.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that in the ground frame, no external force acts on the door, raising questions about how it closes.
  • Others propose that a pseudo force exists when considering the door from the car's frame of reference.
  • There is a discussion about the role of the hinge, with one participant noting that forces at the hinge can both accelerate and rotate the door.
  • Participants question the axis of rotation in the ground frame, with one asserting that it is not obvious and requires mathematical resolution.
  • Some express confusion about how a forward force at the hinge can result in a backward rotation of the door.
  • There is a query regarding the movement of the center of mass of the door relative to the ground during this process.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the forces acting on the door or the mechanics of its closing. Multiple competing views and uncertainties remain regarding the explanation of the phenomenon.

Contextual Notes

Participants highlight the complexity of the problem, noting that assumptions about frames of reference and the definition of forces may influence the discussion. The need for mathematical analysis to clarify the axis of rotation is also mentioned.

Einstein1729
Explain the phenomenon of closing of door of a car when car starts accelerating forward please explain in ground frame.
 
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What forces do you think might be acting on the door ?
 
Nidum said:
What forces do you think might be acting on the door ?
In ground frame I think no force.But wrt to car frame there is one pseudo force.
 
Einstein1729 said:
In ground frame I think no force.
Wouldn't that mean the door would be left behind by the car? :wink:
 
The question is hard to answer in part because the title is no help, you need to use plain English, the question is not very clear.
Please take the time to read the rules about how to post.

Thanks.
 
Einstein1729 said:
In ground frame I think no force.
sophiecentaur said:
Wouldn't that mean the door would be left behind by the car? :wink:
I know that's why I want to know how it closes? Wrt ground frame
 
Einstein1729 said:
I know that's why I want to know how it closes? Wrt ground frame
Does the door have hinges?
 
jbriggs444 said:
Does the door have hinges?
Yes
 
Einstein1729 said:
Explain the phenomenon of closing of door of a car when car starts accelerating forward please explain in ground frame.
In the ground frame the force at the hinge both accelerates and rotates the door. It is important to recognize that the hinge is not the axis of rotation since it is accelerating in this frame. Since it is not the axis of rotation, forces at the hinge can generate torque about the axis of rotation.
 
  • #10
Dale said:
In the ground frame the force at the hinge both accelerates and rotates the door. It is important to recognize that the hinge is not the axis of rotation since it is accelerating in this frame. Since it is not the axis of rotation, forces at the hinge can generate torque about the axis of rotation.
What is the axis of rotation in case of ground frame?and how is the force be able to rotate backward if the force at hinge is in forward? I am sorry if I am wrong.
 
  • #11
Einstein1729 said:
What is the axis of rotation in case of ground frame?
You have to solve for it mathematically, it is not obvious.

Einstein1729 said:
how is the force be able to rotate backward if the force at hinge is in forward?
As long as the axis is anywhere outside the car, the forward force will rotate the door closed.
 
  • #12
Einstein1729 said:
how is the force be able to rotate backward if the force at hinge is in forward?

Does the centre of mass of the door move "backwards" relative to the ground?
 

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