Let $\mathbf{v} = v \hat{\mathbf{x}}$ denote the velocity of the car. Let $\mathbf{u} = u \mathbf{y}$ denote the velocity of the ball relative to the car. Both $u$ and $v$ are constants. The velocity of the ball is therefore constant and equal to $v \hat{\mathbf{x}}+u \mathbf{y}$ . So, answer (B) is correct.

Solution to 2008 Problem 1