two speedboats are racing on a lake. In 10 seconds, Boat A goes from traveling east at 15 m/s to traveling north at 20 m/s. In the same time interval, Boat B goes from 20 m/s east to 25 m/s east.

A student watching the race states: “These two boats have the same acceleration for the 10-second interval since they both changed their velocities by 5 m/s in that time interval.”

What, if anything, is wrong with this student’s contention? If something is wrong, identify it and explain how to correct it. If the contention is correct, explain why.