MLA Citation: Bloomfield, Louis A. "Question 36"How Everything Works 18 Jan 2018. 18 Jan 2018 .
36. Why on Pg. 6, 2nd full paragraph, it says the car is accelerating if the slope of the road changes but in the "not accelerating" list it says a bicycle going up a hill is not accelerating. Aren't those the same situation?
Here is why the two situations are different:

In the first case, the car is traveling on a road with a changing slope. Because the road's slope changes, the car's direction of travel must change. Since velocity includes direction of travel, the car's velocity must change. In short, the car must accelerate. Picture a hill that gradually becomes steeper and steeper—the car's velocity changes from almost horizontal to almost vertical as the slope changes.

In the second case, the bicycle is climbing a smooth, straight hill at a steady speed. Since the hill is smooth and straight, its slope is not changing. Since the bicycle experiences no change in its direction of travel or its speed, it is traveling at a constant velocity and is not accelerating.