路程问题

The distance problem estimates total distance by dividing the velocity-time graph into small rectangular intervals. Each velocity measurement is multiplied by a short time step, then all results are summed. For example, a runner's velocity measured every half-second from 0 to 6.2 meters per second yields displacement estimates by adding these small intervals together.

Left endpoint estimates use velocities at the start of each time interval, while right endpoint estimates use velocities at the end. For a runner accelerating over three seconds with half-second measurements, the left endpoint method yields approximately 10.55 meters, whereas the right endpoint method produces about 13.65 meters. The true distance lies between these two estimates.

More frequent measurements reduce the gap between upper and lower estimates by creating narrower time intervals. As measurements increase toward infinity, the rectangular approximations converge to the exact area under the velocity curve. This limiting process eliminates approximation error and yields the precise total distance traveled.

The distance problem demonstrates that total distance equals the area under the velocity-time curve. When time intervals become infinitesimally small, the sum of velocity multiplied by time intervals converges to the definite integral of velocity over time. This relationship shows how numerical summation methods lead to the integral definition.

A Riemann sum approximates total distance by summing rectangles under the velocity curve. Each rectangle's height represents velocity at a chosen point within a time interval, and its width is the time step. The lower sum uses left endpoints, the upper sum uses right endpoints, and both converge to the integral as intervals shrink infinitely small.

Once velocity is expressed as a function, the fundamental theorem of calculus states that the integral of velocity over time equals the antiderivative evaluated at the endpoints. This provides an exact solution without numerical approximation. The distance problem illustrates why integration is essential for solving real-world motion problems precisely.

The exact displacement is found by taking the limit of the sum of velocity values multiplied by small time intervals as the number of measurements approaches infinity. This limiting process transforms the discrete numerical summation into a continuous integral, providing the precise distance without approximation error.