Translating motion graphs. Dt to vt

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Translating a position-time graph to a velocity-time graph involves understanding the nature of the curves and lines present. A curved line indicates accelerated motion, which translates to a diagonal line in the velocity-time graph, reflecting a constant rate of change in velocity. Conversely, a straight diagonal line in the position-time graph represents constant velocity, leading to a horizontal line in the velocity-time graph. A step function is only applicable when there are two segments of constant speed with an instantaneous change in velocity. Therefore, the confusion regarding the use of a step function in this context is clarified by recognizing the relationship between the types of motion represented in the graphs.
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I am so confuse! It's regarding translating motion graphs.

When translating a position time graph to a velocity time graph, if a curve line is followed by a straight diagonal line (both going up) do I use a step function?

Cause in this video http://m.youtube.com/#/watch?v=EZXLkAYjmR0&desktop_uri=/watch?v=EZXLkAYjmR0

At 3:04. He drew a diagnal line without calculating the slope... Isn't he suppose to use a step function?
 
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kencamarador said:
I am so confuse! It's regarding translating motion graphs.

When translating a position time graph to a velocity time graph, if a curve line is followed by a straight diagonal line (both going up) do I use a step function?

Cause in this video http://m.youtube.com/#/watch?v=EZXLkAYjmR0&desktop_uri=/watch?v=EZXLkAYjmR0

At 3:04. He drew a diagnal line without calculating the slope... Isn't he suppose to use a step function?

The two sloping sections before and after the curved line can be used to find the constant velocities before and after the acceleration section. The presenter has possibly assumed [for simlicity] that the acceleration between those two sections was constant. Does the curved section look like it may be parabolic? [I can't play the video].
 
kencamarador said:
He drew a diagnal line without calculating the slope... Isn't he suppose to use a step function?

No, he souldn't use a step function in such a case.
Curve line in d-t representation means accelerated motion (suppose the curve line is a parabola for simplicity, i.e. uniform acceleration)... then in the v-t representation it is a diagonal line, meaning that velocity is changing at constant rate.

Then the diagonal line in d-t representation means constant velocity. In v-t representation this is instead a straight horizontal line.

Therefore what you get is a diagonal line joined to an horizontal line. You would have a step function in v-t representation only in case you have two motions both at constant speed but with different speed (and at some point speed has to change instantaneously but you do not know why, it is not a realistic situation of course); in this case the d-t representation would be just two diagonal lines with different slopes.
 

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