Solving Vectors: Tips and Tricks for Effective Problem Solving

[link107]

Homework Statement

A man walks 5 m at 37degrees north of east and then 10 m at 60degrees
west of north. What is the magnitude and direction of his net
displacement

The answer is around 9.3m at around 120 degrees angle on the +x axis

Homework Equations

none

The Attempt at a Solution

http://img825.imageshack.us/img825/2570/vectors2.png

I have no idea what to do after I plot out the vector and connect tip to head. Can someone explain to me how to solve for vectors effectively?

Thank you

 

[phinds]

One way to go after it is to draw right triangles and use them to find the end points in XY coordinates of what you have in the drawing. See if you can figure out what I'm talking about.

 

[Draco27]

Another way is to resolve the vectors along x and y axis

5m 37degrees north of east can be written as cos(37)*5 along x-axis and sin(37)*5 along y-axis

similarly do it for other vector..

now add components along x and y-axis separately and get new measurements along x and y axis

now use x²+y² = (magnitude of resultant)²
for magnitude

and arctan(y/x) for direction of resultant vector.(x and y are values of new measurements along x and y axis) (angle obtained is the angle from +ve x axis)

 

[voko]

now use x²+y² = (magnitude of resultant)²
for magnitude

You really surprise me. You can't figure out how to obtain the distance between two points given their coordinates, yet you advise others precisely on how this is done.

 

[Draco27]

Did i make a mistake??

 

[voko]

Did i make a mistake??

No you did not. That's why I am surprised. Why can't you apply this same knowledge to your problem about the moment of inertia?

 

[Draco27]

Basically i got it

But pls help me with the double integration

i mean how is it done??