# Vector Question any suggestions?

#### kara

A plane flies 483 km east from city A to city B in 45.0 min and then 966 kim south from city B to city C in 1.50 h. For the total trip, what are the magnitude and direction of the plane's displacement, the magnitude and direction of its average velocity, and its average speed?

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#### Hootenanny

Staff Emeritus
Science Advisor
Gold Member
It may be helpful to draw a diagram. Some pythag and trig may also be required...

#### radou

Homework Helper
All you need is some simple vector addition:http://www.codesampler.com/d3dbook/chapter_02/chapter_02_files/image012.jpg" [Broken].

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#### kara

Would this be correct:

I calculated r the distance between points A and C by r = (483 km) + (- 966 km) to get - 483 km
So the planes magnitude was 483 km in the negative direction, or south east. Is this correct?

#### kara

Basic physics help

A plane flies 483 km east from city A to city B in 45.0 min and then 966 kim south from city B to city C in 1.50 h. For the total trip, what are the magnitude and direction of the plane's displacement, the magnitude and direction of its average velocity, and its average speed?

Would this be correct:

I calculated r the distance between points A and C by r = (483 km) + (- 966 km) to get - 483 km
So the planes magnitude was 483 km in the negative direction, or south east. Is this correct?

#### radou

Homework Helper
kara said:
A plane flies 483 km east from city A to city B in 45.0 min and then 966 kim south from city B to city C in 1.50 h. For the total trip, what are the magnitude and direction of the plane's displacement, the magnitude and direction of its average velocity, and its average speed?

Would this be correct:

I calculated r the distance between points A and C by r = (483 km) + (- 966 km) to get - 483 km
So the planes magnitude was 483 km in the negative direction, or south east. Is this correct?
Nope, use Pythagoras's theorem to calculate the magnitude of the total displacement of the plane.

#### kara

ok.. so i used pythagorean theorem and got this:

r = 1080.020833 which i'll round to 1080 for 4 sig figs.

Now finding r gave the the magnitude would i use the tan formula to find direction???

#### radou

Homework Helper
kara said:
ok.. so i used pythagorean theorem and got this:

r = 1080.020833 which i'll round to 1080 for 4 sig figs.

Now finding r gave the the magnitude would i use the tan formula to find direction???
Exactly. By the way, the 'arrow' points from A to C.

#### kara

Basic physics help

ok.. so i used pythagorean theorem and got this:

r = 1080.020833 which i'll round to 1080 for 4 sig figs.

Now finding r gave the the magnitude would i use the tan formula to find direction???

now i found the angle to be = tan-1 (966/483) and got 63.4 * but how do i know what direction its in???
If i draw the diagram on the cartesian plane i get the final location of the plane to be in the -y +x coordinate, so it would be in the south east direction??? am i right???

#### kara

based on your last reply, whats the definition for magnitude?
b/c now i've got to find magnitude and direction for average velocity and then average speed

#### radou

Homework Helper
kara said:
...
If i draw the diagram on the cartesian plane i get the final location of the plane to be in the -y +x coordinate, so it would be in the south east direction??? am i right???
Yes, you're right. Again, look at the vector addition rule I linked somewhere above, it should make everything clear.

#### kara

Basic physics help

Alright, so to find the magnitude and direction of the plane's average velocity i used the vave = delta r/delta t formula to find average velocity for vx and vy and then i used pythagorean theorem to find v and i got 910.8 km/h... does that make any sense? Now im assuming the direction would be exactly the same as before. And how do i calculate average speed?

#### radou

Homework Helper
Here, this link should be useful: http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/1DKin/U1L1d.html" [Broken].

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#### kara

Alright so based on the website you provided and my notes i calculated the average speed to be 644 km/h and the average velocity to be 214.7 km/h in the south east direction.

v = (483 + 966)/2.25 = 644 km/h

vave = (966-483)/2.25 = 214.7 km/h south east

What do you think??

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