Net Displacement: Subtracting E from W Direction Vectors

[ybhathena]

Is it valid to subtract a position vector of direction E with one of direction W or do they both have to have the same dierction when using the net displacement formula?

 

[Doc Al]

Is it valid to subtract a position vector of direction E with one of direction W or do they both have to have the same dierction when using the net displacement formula?

They must be treated as vectors. 10 units E minus 10 units W does not equal zero, if that's what you're thinking. (You can only subtract components that are along the same direction.)

 

[mathman]

If they are in opposite directions, you can subtract. If E and W mean East and West, you can subtract.

 

[Doc Al]

If they are in opposite directions, you can subtract. If E and W mean East and West, you can subtract.

Good point! For some reason, I was thinking of East and South, but I'm sure you're right that it means East and West. Good catch. (Oops!)

 

[Doc Al]

Is it valid to subtract a position vector of direction E with one of direction W or do they both have to have the same dierction when using the net displacement formula?

Let me answer it again, given mathman's clarification:

Yes, you can subtract them since they are parallel. But realize that 10 units W is the same as -10 units E. So 10 E - 10 W = 10 E - (-10 E) = 20 units E.

Make sense?

(Glad that mathman was awake.)

 

[Boston_Guy]

Is it valid to subtract a position vector of direction E with one of direction W or do they both have to have the same dierction when using the net displacement formula?

In your mind, what is the physical interpretation of the addition/subtraction of such position vectors?

 

[jbriggs444]

If I drive 10 miles east, turn around, put the car in reverse and drive another 10 miles while facing west, the result is 20 miles traveled to the east.