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plz explain pseudo force in detail and give example
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a pseudo force is nothing but a force which is needed to be taken while working problems in non inertial frame. ok,what is non inertial frame? it is the frame which is accelerated. for eg.u are standing inside a lift which is going upward with an acceleration "a". when u measure ur weight it will not show the actual weight. u get ur answer wrong if u simply say my weight is mg inside the lift. Lift is a non inertial frame.so u need to apply a pseudo force opposite to the direction of acceleration. ie,ma downward.u must say that ur wt is m(a+g) which is shown by the machine. 2.another interesting eg is that ,when u are standing inside a bus ,u may experiance a sudden jerk backward when the driver starts the vehicle .why is it so?no one is pushing u backwards .it is only the pseudo force which did this job. i thing u have got a clear picture of what a pseudo force is. |
A frame of reference which is moving with an acceleration w.r.t. the system of fixed stars is called a non inertial frame of reference or an accelerated frame of reference. In this accelerated frame of reference, Newton's laws of motion are not valid. In an inertial frame, we consider real forces, but in non-inertial frames we introduce the concept of fictitious or pseudo forces. These forces are not due to any interaction between two bodies, but they arise due to the acceleration of the reference frame.
Concept of Pseudo force is introduced so that Newton's laws of motion (Laws of inertial frames) can be applied to situations in non-inertial frames. Pseudo force is assumed to act in a direction opposite lo the direction of acceleration of the reference frame. In a frame of reference moving with an acceleration (w.r.t. inertial reference frame), the pseudo force acting on a body is equal to -map • e.g. when a car takes a turn, a passenger sitting in the car experiences a force in the radially outward direction. This is a pseudo force called the centrifugal force (directed' away from the centre).
Suppose that a man is standing on a merry go round or on a heavy turn table rotating uniformly in a horizontal plane. He performs a U.C.M. As U.C.M. is an accelerated motion, his frame of reference is an accelerated or a non-inertial frame. For an outside observer at rest, the person on the turn table moves along a circle because of a centripetal force. The man on the turn table feels that at every instant he is acted upon by a force which is directed along the radius but away from the centre. Such a force experienced by a non-inertial observer is called a centrifugal (away from the centre) force. The outward force which is felt by an observer in the rotating frame of reference is called a centrifugal force. It is a pseudo force.
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In a closed moving train, moving with uniform velocity with respect to an observer on a station, the person in the train - here after we shall denote the person by the symbol A- will not know that he is moving.
A bob suspended by as string from the ceiling of the train will be vertical to the floor of the train.
Suppose the train now begins to accelerate. The bob will turn through an angle θ to the vertical. Since the train is a close one, A will infer from this this change in the vertical direction that his train is accelerating. He can calculate the acceleration from the angle and hence he will apply a force equal to mass times this acceleration to all the objects in his train.
This force is not the result of reaction force as far as A is concerned To apply Newton's laws of motion which is for inertial frames of reference, A applies this force to all objects in his train and thus makes his frame equivalent to an inertial frame.
This force which is not as a result of action reaction force [ with respect to A] is called pseudo force.