Continental Hot Spots – Yellowstone Hot-Spot Trail. Use the Path tab on the Ruler tool to measure the distance between the Problem 21 placemarks (cm) along the hot-spot trail. Calculate the average velocity of the North American Plate in cm per year, using 16.5 Ma and 0.63 Ma for the two placemarks. a) ~1.9 cm per year
b) ~4.2 cm per year
c) ~8.8 cm per year
d) ~15 cm per year

Answertraveling around a circular trackexplanation"traveling around a circular track" is the best answer as you could be traveling around a circular track at a constant speed. your velocity would therefore have the same magnitude but will always be constantly direction. since acceleration is the rate of change of velocity, the rate of change will only involve the direction of velocity and not the magnitude.wrong choices: "an object at rest" does not accelerate at all"increasing speed while traveling around a curve" means that the acceleration will not be constant due to only change in direction; it will be constant due to both magnitude and direction"an object in free fall" does not necessarily change direction 

Special care would be an answer

Athermometer to measure the temperature of course