Answer to Question #118906 in Classical Mechanics for Lizwi

Question

If a small ball is moving at constant velocity, v, in the plane of the paper. If there are no external forces acting on the ball, describe the path of the ball in terms of the position,r, and velocity, v, of the ball.

Answer 1

According to Newton's first law, the ball will move in a straight line and will not change its velocity, or

$$\vec{r}(t)=\vec{r}_0+\vec{v}t.$$