A physics professor leaves her house and walks along the sidewalk toward campus. After 5 min it starts to rain, and she returns home. Her distance from her house as a function of time is shown in Fig. E2.10. At which of the labeled points is her velocity (a) zero?

Video transcript

Hey everybody. So today we're dealing with a position versus time graph and we're told that a worker is driving home from the office place after 13.5 minutes, he realizes that he forgot some documents back at the office and returns to the office place. Now the workers distance from the workplace is depicted as this position versus time graph. But we're asking or we're being asked what point represents zero velocity. Now let us recall that on a position versus time graph or or well, if we are to just ask like if we wanted to find the slope on this position versus time graph, right. Well, that would be the change in why the change in the y direction divided by the change in the X direction, right? And I'm gonna write my ex like this for now and you'll see why in a second. But if we have to translate that to what the variables are here, we get that. This is the change in the position divided by change in time, which is just simply the definition of velocity. Therefore the slope of a position versus time graph is nothing but the velocity at that point. So if we want to find zero velocity, what we need to find, where is the slope equal to zero. And there's only one point on this graph where the slope is indeed equal to zero and that's at point B right? It is a flat lining for to find the slope here. Well, it would just be zero because again it is flat, there's no rise, it's not going down, it's not positive, it's not negative, it is zero. Which means the answer choice here, which is a little convoluted. I suppose the answer choice you need to select this answer choice A. Which sites option B or point B as the point that represents zero velocity. I hope this helps. And I look forward to seeing you all in the next one.