# The Gravitational Field

1. Sep 10, 2011

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

But as you can see, when I typed the answer on the answer column, the computer marked it as wrong. Please point out my mistake in 24 hours. Thank you.

Last edited: Sep 10, 2011
2. Sep 10, 2011

### lewando

What is the distance between M and O?

3. Sep 10, 2011

By simple Pythagorean theorem you can work it out to l^2 sqrt{2}

4. Sep 10, 2011

### lewando

I get something different. Since the clock is ticking, how about
$$l \sqrt{2}$$

5. Sep 10, 2011

I was writing the distance squared. So basically our answer for that is same.

6. Sep 10, 2011

### lewando

Ahh.. nevermind me, I thought I saw it... standby please.

7. Sep 10, 2011

I think my answer is correct and the computer is wrong.

8. Sep 10, 2011

### lewando

How about your last step? The answer you gave was the common coefficient of i and j. But to get the magnitude should you not take the root of sum of the squares of these coefficients?

Last edited: Sep 10, 2011
9. Sep 10, 2011

### WatermelonPig

Use more sets of parentheses at the beginning.

10. Sep 12, 2011

Enlighten me.

11. Sep 12, 2011

### Hootenanny

Staff Emeritus
What is the magnitude of the vector $\boldsymbol{x} = \boldsymbol{i}+\boldsymbol{j} = [1,1]^\text{T}$?

12. Sep 12, 2011

### stallionx

When something is in the form Constant * ( i + j ) and you would like to find the magnitude of that

use abs ( Constant * ( i+j) ) = Abs(Constant ) * Abs(i+j)

what is Abs ( i + j ) ?

How would you interpret it ?