A physical problem with the nature of motion Does the velocity of horizontal uniform linear motion and vertical uniform linear motion keep the same Doesn't it mean that the velocity perpendicular to the direction of acceleration doesn't change

A physical problem with the nature of motion Does the velocity of horizontal uniform linear motion and vertical uniform linear motion keep the same Doesn't it mean that the velocity perpendicular to the direction of acceleration doesn't change

Analysis:
After reading your question, I find that you have a misunderstanding
In other words, "the velocity perpendicular to the direction of velocity and acceleration does not change." in this paper, both velocity and acceleration refer to combined velocity and combined acceleration. Therefore, the horizontal direction makes a uniform linear motion, and the vertical direction makes the most uniform linear motion. Its combined velocity is not horizontal or vertical, but has a certain angle with the horizontal and vertical direction, And the resultant acceleration of its motion is vertical, so it can be found that the resultant velocity and resultant acceleration are not vertical, so it should be "uniform linear motion in the horizontal direction, uniform linear motion in the vertical direction, the resultant velocity must change."
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