# Homework Help: Assistance with physics vector problem

1. Jan 20, 2009

### -EquinoX-

1. The problem statement, all variables and given/known data

Give the components of the velocity vector for wind blowing at 12 km/hr toward the southeast

2. Relevant equations

3. The attempt at a solution

12cos(45)i - 12sin(45)j

Isn't this right?

2. Jan 20, 2009

### TVP45

Re: vectors

Two observations.
It's not clear what i and j represent. Sure, I'm about 99% certain I know what you mean, but I shouldn't have to guess.
If you break a velocity into its components, are those components also velocities?

3. Jan 20, 2009

### -EquinoX-

Re: vectors

i is the vector direction that represents the x axis and y is the vector direction that represents the y axis.

and yes those components are also velocities

4. Jan 20, 2009

### TVP45

Re: vectors

Yes, I was sure you mean those directions, but it is not universally understood that i
means east. And, the components shown in your answer are not velocities.

5. Jan 20, 2009

### -EquinoX-

Re: vectors

so if it's not velocities then what is it? and how do I represent it in velocities?

6. Jan 20, 2009

### TVP45

Re: vectors

OK, we agree the components of a velocity should also be velocities. Your original velocity is a vector. Look at your components and ask whether they satisfy the requirements of a velocity vector.

7. Jan 20, 2009

### -EquinoX-

Re: vectors

i still dont see it why its not a velocity vector

8. Jan 20, 2009

### TVP45

9. Jan 21, 2009

### Unco

Re: vectors

We have the magnitude and the direction of a 2D vector (who cares if it happens to represent velocity?), and we want to resolve it into its x and y components. Equi has done this; what's up, TVP?

10. Jan 21, 2009

### TVP45

Re: vectors

Not to be too pedantic about this, but 8.48 east is not a velocity. The magnitude of such a velocity will always consist of a number (8.48) and a unit (km/hr). While you can set up a situation where the unit is either implied or else not needed, this is not the case here. The statement of question asks about a wind blowing to the SE and, in this instance, velocity has a real physical meaning as a ratio of distance to time and that requires a unit.