The child is the moving point on the curve. The child can push and pull, which can be understood as the stick is hinged on the toy, and the toy always keeps a distance from the child. Tension (thrust) is always in the tangent direction of the curve.
Imagine that if a child walks in a straight line and pulls a toy, it is obvious that the toy also walks in a straight line, and the trajectory coincides with the child's route. When the direction changes (dotted line), the toy will temporarily deviate from the track, but will eventually return to the child's track.
If the straight line of the broken line is infinitely small, then the trajectory of the toy will completely coincide with the broken line. If it is pushing, the child will trick up to the normal A of his trajectory when turning, and then turn to pull.
Extended data curve motion
(1) Velocity direction: the velocity direction of a particle at a certain point, along the tangent direction of the curve at that point.
(2) Nature of motion: The speed direction of an object moving on a curve is always changing, so the curve motion must be variable.
(3) Conditions of curvilinear motion:
Judgment of exchange rate change
(1) When the direction of external force forms an acute angle with the direction of velocity, the velocity of the object increases;
(2) When the included angle between the external force direction and the speed direction is obtuse, the speed of the object decreases;
(3) When the direction of external force is perpendicular to the speed direction, the speed of the object is constant.