Final answer:
The motion of a rock thrown straight up involves acceleration due to gravity, zero velocity at the peak, and differences between average velocity/displacement and average speed/distance.
Step-by-step explanation:
When a rock is thrown straight up into the air, it experiences a variety of motions characterized by terms such as acceleration, average velocity, average speed, distance, and displacement. On its way up and down, the rock is subjected to a constant acceleration due to gravity, which is typically -9.8 m/s2 (the negative sign indicates that gravity is pulling the rock downward). At the top of its flight, the velocity of the rock is zero for a brief instant before it begins to fall back down.
Differentiating between average velocity and average speed, the former is displacement divided by time, which can be zero if the rock returns to its original launch position, while the latter is the total distance traveled divided by time and will always be positive. The distance the rock travels is the path length it covers, which is twice the height of its trajectory if it lands back at the starting point. In contrast, the displacement is a vector quantity that measures the straight-line distance from the starting point to the final position, which could be zero if the rock returns to where it started.