This is the boss. No calculator, and every value is chosen to fit in your head. One cart, one ramp, and every answer feeds the next: the acceleration from the sensor, then the speed at the bottom, then the length of the ramp, then the total time of the run. Write each line down as you go — one early slip rolls all the way to the floor.

Every relation in the chapter rides along. The acceleration is a rate of change; the speed at the bottom is that rate accumulated; the ramp is the area under the velocity line; and the coast along the flat is the average-velocity form in its easiest possible case, where the two speeds are equal and the average of a number with itself is just the number. Then the bonus mark asks for something no arithmetic can give you on its own: a verdict.

5★ under par here is the chapter crown. Clock in.