Projectile Motion - smol question about velocity (1 Viewer)

[gamja]

on such graph, impact velocity is 10sqrt21 from formula v^2 = xdot^2+ydot^2.

I was just wondering, how do you know if we take the positive (as in this case) or the negative velocity?

Thanks so much for your help!





[edit:]

Wait... maybe the answers supposed to be negative 10sqrt21 from negative gradient on that displacement/time graph?
And also from the diagram below?
]

 

[cossine]

View attachment 37465
on such graph, impact velocity is 10sqrt21 from formula v^2 = xdot^2+ydot^2.

I was just wondering, how do you know if we take the positive (as in this case) or the negative velocity?

Thanks so much for your help!





[edit:]

Wait... maybe the answers supposed to be negative 10sqrt21 from negative gradient on that displacement/time graph?
And also from the diagram below?
View attachment 37466]

Generally we consider velocity for a 1-D dimensional case. That is on some straight line. E.g. the velocity of car on a road with respect to some origin.

The issue with including multiple dimensions such as 2D is there are infinite number of directions that can be traveled. Any angle from 0-360.

For this reason the velocity is broken into components such as xdot, ydot or represented as a vector.

To summarise N-dimensional velocity cannot be represented by a single number. What you seem to be referring to is speed. As speed is always positive you will take the positive square root.