A skateboard is moving westward and its speed is increasing. Two students discuss the situation.
Student A: “The acceleration must be negative because the skateboard is going towards the west.”
Student B: “The acceleration must be positive because the skateboard’s speed is increasing.”
(i) If east is taken as the positive direction, explain which student is correct. Support your answer by referring to the signs of velocity and acceleration.
(ii) If the positive direction is now chosen towards the west, what would be the algebraic signs of the velocity and the acceleration of the skateboard? State whether in this new convention the skateboard is said to have positive acceleration or negative acceleration, and justify your answer.