A car that is stopped at a light starts and goes faster each second. A driver who sees a child brakes hard. In this course we define acceleration, we read the velocity-time graph and find the distance from its area, and we get three equations that solve most problems of motion with a constant acceleration, such as the braking distance of a car.
3 lessons, about 1 h 15 min3 simulations12 problems6 practice questionsPython in every lesson
Acceleration is the rate of change of velocity, , in . It speeds a body up when it points the same way as the velocity, and slows it down when it points the other way. On a velocity-time graph, the slope is the acceleration and the area under the line is the displacement (area below the time axis counts as negative).
For a steady acceleration, three equations link , , , and : , and . Each comes from the velocity-time graph. Choose the one that leaves out the quantity you neither know nor want, and keep one sign convention for every vector.
A car's stopping distance is the thinking distance, , covered at full speed during the reaction time, plus the braking distance, . Because the braking distance grows as the square of the speed, a little more speed needs a lot more road. From rest with a steady acceleration, the distance in the th second is , so successive seconds cover distances in the ratio
Log in to join the discussion.
Loading…