# Average Resultant Force

1. Nov 5, 2007

### jack1234

[SOLVED] Average Resultant Force

Hi for this question
http://tinyurl.com/3cbxlq

What I try is
Average Force
=(mv-mu)/t
=2000(6-4)/4
=1000
but this is not one of the answers. Meaning it is wrong.

May I know how to do this question?

2. Nov 5, 2007

### Staff: Mentor

Well one has to take the difference between two vectors which are orthogonal (90°). So find the resultant vector and divide by the time to obtain the average acceleration.

$$\frac{\Delta\vec{F}}{\Delta{t}}\,=\,m\frac{\vec{v_f}-\vec{v_i}}{\Delta{t}}$$

Assume the truck's initial speed is 6 i m/s and it takes a right turn and has speed 4 j m/s, where i and j are unit vectors in the x and y directions

Last edited: Nov 5, 2007
3. Nov 5, 2007

### jack1234

Got it, thanks :) Using magnitude of vector to get the answer, it is c.

4. Nov 5, 2007

Correct!