# Homework Help: A couple basic physics questions(vector sum and kinematics)

1. Sep 15, 2011

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

I already know the answers because this is a review sheet, but I don't understand how to solve number 1, and I don't understand the wording of number 2.

1) A particle is moving along the x-axis and has a position given by x=(24t-2.0t3)m, where t is in seconds. How far is the particle from the origin (x=0) at the time when the particle is not moving.

answer is t=32 seconds, but I don't quite know how to solve for t this way.

2) A vector B, when added to vector C= 3i + 4j yields a resultant vector which is in the positive y-direction and has a magnitude equal to that of vector C. What is the magnitude of B?

I know how to add vectors, but I don't understand the wording here.

Thanks.

2. Sep 15, 2011

### SteamKing

Staff Emeritus
1) When the particle is not moving, what is its velocity?

2) Assume vector B = xi + yj. |B+C| = |C| and the i-component of B+C is zero.

3. Sep 15, 2011