When an car moves forward we go back and we have always read that the reason was that our legs stay in contact with the ground and our body goes back since it was at rest and with sudden motion it still has a tendency to stay at rest . But shouldn’t pseudo force apply too ? I did asked someone that and they said that pseudo force is a result of inertia. If that’s the case how do we say that pseudo force is a result of inertia in the case of centripetal force and in the case of a lift ? I am asking if in a standing bus we go back due to pseudo force or do we go back due to inertia or both ?
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2It is due to inertia. Pseudo-force is just a mathematical tool one uses if one is observing an object's motion from a non-inertial frame. – Pumpkin_Star Feb 10 '24 at 12:29
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Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. – Community Feb 10 '24 at 13:54
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This is about Coriolis force, but it should clarify pseudo force. Coriolis Force: Direction Perpendicular to Rotation Axis Visualization – mmesser314 Feb 10 '24 at 15:48
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If pseudo force is just a mathematical tool used to observe motion in an non inertial frame and the person going back in the bus is due to inertia , how do you explain us feeling lesser weight when. An lift goes down ? Where does inertia come there ? – Aditya Pradhan Feb 11 '24 at 04:31
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Our bodies are not rigid. When you are standing in a stationary lift, notice how you primarily feel more pressure or weight or strain in your feet and legs than the top of your head. This is because at the bottom of your feet you tissues get compressed a bit because of your body's weight and the normal force exerted by the floor. This compression is what causes you to feel weight. Now suppose the lift starts accelerating downwards with acceleration a<g. Now the normal force exerted on your body is less, so the tissues compress less and so you feel less weight. Now if you free fall.... – Pumpkin_Star Feb 11 '24 at 05:21
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.....then normal force is 0. All the molecules of your body are accelerating with acceleration g. Your tissues are under no compression so you feel weightless. – Pumpkin_Star Feb 11 '24 at 05:22
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But suppose you tie your feet down to the lift's floor and the lift starts accelerating downwards with a force more than g. Then you will feel as if a force is pushing you upwards. This is because your body is being stretched upwards. Your muscles are pulling your upperbody downwards. – Pumpkin_Star Feb 11 '24 at 05:29
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Similarly, in your bus example, If the bus accelerates forward, the friction between your feet and the bus's floor will apply a force on your feet to give it the same acceleration as that of the bus. However, your upper body is thrown back because of inertia. As your upper body is thrown back, your muscles stretch and then apply force to provide your Upper body with the same acceleration that your feet have. So, in short, your body is thrown back because of inertia, but the pull you feel is because of your muscles stretching. – Pumpkin_Star Feb 11 '24 at 05:41
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Newtonian mechanics favors the description of mechanical phenomena in inertial reference frames. However, it also allows an equivalent but differently stated description in accelerated reference frames. These two possibilities should never be mixed to avoid confusion and conceptual mistakes.
In the case of a car accelerating forward and the passenger inside, in an inertial reference frame, one describes the effect on the passenger as the effect of the force applied by the accelerating structure of the car on some part of the passenger's body in contact with it. Such force modifies the velocity of the passenger that otherwise would remain constant by inertia.
In the non-inertial reference system of the car, the same effect is due to the presence of a pseudo-force acting on all the bodies in the car in the direction opposite to the direction of acceleration (in the inertial reference frame).
