5. A particle moves in a circular path of radius r with speed v. It then increases its speed to 2v while traveling along the same circular path. By what factor has the period of the particle changed? (а) 0.25 (b) 0.5 (c) 2 (d) 4 (e) impossible to determine (f) none 6. A particle moves along a path, and its speed increases with time. In which of the following cases are its acceleration and velocity vectors parallel? a) when the path is circular b) when the path is straight c) when the path is a parabola d) never 7. As a projectile thrown at an upward angle moves in its parabolic path (such as in the figure), at what point along its path are the velocity and acceleration vectors for the projectile perpendicular to each other? (a) nowhere (b) the highest point (c) the launch point (d) never (e) none

5. A particle moves in a circular path of radius r with speed v. It then increases its speed to 2v while traveling along the same circular path. By what factor has the period of the particle changed? (а) 0.25 (b) 0.5 (c) 2 (d) 4 (e) impossible to determine (f) none 6. A particle moves along a path, and its speed increases with time. In which of the following cases are its acceleration and velocity vectors parallel? a) when the path is circular b) when the path is straight c) when the path is a parabola d) never 7. As a projectile thrown at an upward angle moves in its parabolic path (such as in the figure), at what point along its path are the velocity and acceleration vectors for the projectile perpendicular to each other? (a) nowhere (b) the highest point (c) the launch point (d) never (e) none