# Word Problem.Is this correct?

....got it....

Thnx though!

Last edited:

#### csprof2000

Check this out.

x: person's x position
y: person's y position
X: raptor's x position
Y: raptor's y position

x = 5(sqrt2) (t+3)
y = 5(sqrt2) (t+3)

X = 12(sqrt2) t_x
Y = 12(sqrt2) t_y

If the raptor wants to catch you, t_x must equal t_y... because the person is on the line x=y and the raptor starts at the origin. So t_x equals t_y equals t.

Let T represent the time the raptor catches you (with t = 0 being when the raptor starts running). Then we must have that

5(sqrt2)(T+3) = 12(sqrt2)(T/2)

The equation is the same for y.

Solving for T...

5T + 15 = 6T

T = 15.

So it takes the raptor 15 seconds to catch the dude.

It can't very well be 1.5 s, can it? The raptor has only moved 22.5(sqrt2) = 32 total, while the person has moved 45 total. Even if the raptor was chasing the guy directly, he wouldn't catch him.

#### sutupidmath

Check this out.

X = 12(sqrt2) t_x
Y = 12(sqrt2) t_y

T = 15.

So it takes the raptor 15 seconds to catch the dude.

It can't very well be 1.5 s, can it? The raptor has only moved 22.5(sqrt2) = 32 total, while the person has moved 45 total. Even if the raptor was chasing the guy directly, he wouldn't catch him.
Comparing my solution with yours(the one that i did after my first post), i see that we have the same idea, in general terms with some slight differences, besides that you have a typo on your solution, because the speed of the raptor is 15sqrt{2}m/s and not 12sqrt{2}m/s so the final answer should be 6 s.

Cheers!

Homework Helper
Gold Member
Dearly Missed

#### sutupidmath

It looks like that's the case.

Well, in fact, after i initially posted the problem and the 'solution', after a few hours i wanted to edit it since i found the correct solution, but while tring to post it the pf was having trouble or don't know what, so that's what was left from my post.

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving