A couple basic physics questions(vector sum and kinematics)

[Crusaderking1]

Homework Statement

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.

Answer is 3.2 m.
Thanks.

 

[SteamKing]

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.

 

[Crusaderking1]

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.

1) It is 0. when v=0, t=2, when t=2, m=32 m.

2) crystal clear. thanks.