# A Coordinates and Interval Question

## Homework Statement

During a 4.95 s interval, a particle's coordinates change from x = 10.4 m, y = 4.95 m to x = 31.5 m, y = -4.95 m. Assuming the particle's velocity is constant, what will its coordinates be at the end of the next 4.95 s interval?

x= ____m
y= ____m

## The Attempt at a Solution

My first thought was to take the x and y's given and find y=mx+b however I'm not sure that it is relevant or even helpful.

Thanks.

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CompuChip
Homework Helper
You should consider both directions independently.

So x and y satisfy
x = u t + a,
y = v t + b

Equivalently, the distance covered in the second 4.95 seconds is the same as that covered in the first interval.

CompuChip,

I'm not sure I understand what you're saying. What do the variables represent in your equations? I'm sorry if these are silly questions, however I just finished my second day of Physics and am completely new to it (and also very bad at it!).
Thanks.

berkeman
Mentor
CompuChip is showing the equations of motion for a constant velocity. You can break the problem up into the orthogonal velocities in the x and y directions. So his first equation says that x(t) is equal to x(0) = a, plus an offset given by the velocity u multiplied by the time t.

Does that help?

berkeman,

I understand that much, however I don't understand how those equations work with my numbers?

berkeman
Mentor
berkeman,

I understand that much, however I don't understand how those equations work with my numbers?
You are given a delta-t and a delta-x and a delta-y. From those numbers and those equations, you can figure out what those constants are (u, a, v, b). With those constants and the next delta-t, you can figure out what the final positions will be after the second delta-t.

Thank you, I appreciate your time!

I definitely over analyzed the question. All you do is find the change in x and changed in y and add them to the last x and y coordinates. I didn't have to do anything with time or velocity.

In this case, yes, but what if the next interval was 6.1 seconds. Profs have bbeen known to do such things, esp physics profs!

So knowing the velocities is a necessary skill on the third day.