# Homework Help: Physics-magnitude/ displacement?

1. Sep 13, 2010

### J.live

1. The problem statement, all variables and given/known data
A truck travels 3.45 km north and then makes a 90° left turn and drives another 4.10 km. The whole trip takes 4.50 min.

1)With respect to a two-dimensional coordinate system on the surface of Earth such that the y-axis points north, what is the net displacement vector of the truck for this trip?

2) What is the magnitude of the average velocity for this trip?

3. The attempt at a solution

1) -4.10 i + 3.45j ? Is this right?

2) how will i solve for the magnitude? I mean i know we have to use the distance formula but it didn't work.

If some can explain and show some work in order for me to understand. It will be appreciated

2. Sep 13, 2010

### w3390

So these directions form a 90 degree triangle, where one of the sides is 3.45 km long and the other side is 4.10 km long. However, these are just the components of your displacement. The problem wants to know the distance from start to finish following a straight line. Think A^2+B^2=C^2.

For the second part, you are given the time it takes for the whole trip and you calculated the displacement of the trip. Therefore, you have a distance and a time. What is the relation between velocity, distance, and time?

3. Sep 13, 2010

### J.live

yeah the Pythagorean and theorem.

for the second one, I tried to find the magnitude and divide it by the time but didnt come out right

4. Sep 13, 2010

### w3390

Make sure you make the correct conversions. I don't know what units your answer needs to be in, but it may be km/s, km/hr, or m/s.