# Homework Help: Magnitude of Displacement :P

1. Oct 17, 2004

### star227

Okay i dont have the best physics teacher :-/ he often gets confused with what he's teaching and shows us the wrong thing...We have four problems for homework and I would just like one of you experts to check over it ;)

1. A car is driven 125 km due west, then 65 km due south. What is the magnitude of displacement? R^2=a^2 + b^2
R^2=125^2 + 65^2
R^2=19850
2. A shopper walks from the door of the mall to her car 250m down a lnae of cars, then turns 90 degrees to the right and walks an additional 60m. What is the magnitude of the displacement of her car from the mall door?
R^2=a^2 + b^2
R^2=60^2 + 250^2
R^2=66100
3. A hiker walks 4.5 km in one direction, then makes a 45 degree turn to the right and walks another 6.4 km. What is the magnitude of her displacement?
R^2= a^2 + b^2 - 2ab COS(angle)
R^2= 4.5^2 + 6.4 ^2 -2(4.5)(6.4)cos45
R^2=20.25 + 40.96- 40.729
R^2=20.481
4. What is the magnitude of your displacement when you follow directions that tell you to walk 225 m in one direction, make a 90 degree turn to the left and walk 350 m, then make a 30 degree turn to the right and walk 125 m?
I'm not sure how to go about doing this one but what I DO know is
how the triangle looks and the angle measurements. I'm just not
sure what it is I'm supposed to be writing down. A hand plz lol?

2. Oct 17, 2004

### star227

...would I use the first or second equation? What about a combination of both? ...maybe its a trick question lol maybe its right there you just have to know what it is...

3. Oct 17, 2004

### bross7

You could use both. Get the resultant magnitude (R1) from the first two directions. And then find the resultant (R2) from R1 and the 3rd vector.

4. Oct 17, 2004

### star227

thanks! is the rest of it right?

5. Oct 17, 2004

### star227

isnt the resultant vector 125??? whoaaa...*confused*

6. Oct 17, 2004

### star227

To find the resultant magnitude I would use r2=a2+b2 rite? i dont know what youre talking about the next part that confuses me..3rd vector is 125 correct?

7. Oct 17, 2004

### star227

please someone help my gpa is plummeting thru tha ground ive made 2 awful homework grades recently: 71% and a 76%!!!! :'(