Math Is Fun Forum

Yuri

Guest

Problem involving rate of change of distance.

Two cars start moving form the same place. One goes north at a rate of 50 mi/hr, while the other heads east at a rate of 30 mi/hr. At what rate is the distance between the two cars changing exactly two hours later?

I thought that the equation for the velocity vectors is:

r(x) = 30xi + 50yj

and thus distance d two hours later is given by:

d = √(30x²  + 50x² )

and

dr/dt = ∂x/dt + ∂y/dt

and after solving the equation I just plug in 2 for x and y to get what time the distance changes at the two hour mark.

Is this right?

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Problem involving rate of change of distance.

Hi Yuri,

---

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

Yuri

Guest

Re: Problem involving rate of change of distance.

Thanks a lot.

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Problem involving rate of change of distance.

You're welcome.

---

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."