Motion in a Straight Line

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A frame of reference is an arbitrary reference system with respect to which position and time coordinates of an event are assigned. It is needed because motion is always described relative to somethin…

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Position and time coordinates change with the observer's frame. A physical quantity can have different values in different frames, so the reference frame must be specified to describe motion correctly…

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An inertial reference frame is a frame in which Newton's first law correctly describes motion of a body with no net external force. Such a frame is unaccelerated and non-rotating.

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An aircraft during take-off is accelerated, so the frame itself is not inertial. A non-inertial frame is one that is accelerated or rotating.

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A point object. The person's size is very small compared to the distance covered relative to the train, so the body can be treated as a point mass.

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A point object. Its size is small compared to the distance between the stations, so it can be treated as a point mass.

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No. It is not a point object because its size is comparable to the motion involved when it turns sharply on hitting the ground.

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Distance is the length of the actual path covered and is a scalar quantity. Displacement is the difference between final and initial positions and is a vector quantity.