When exiting off of an interstate, why does the car seem to go from 75mph to 50mph faster than 25mph to 0mph? The road composition, grade of the road, or the tires on the vehicle never changed, yet the car seems to maintain its velocity at the slower speeds.
In: Physics
There are several things going on here. It sounds like you are not the driver, is that correct? Maybe you’re describing your own experience? Not sure.
First, the driver is the one in control of the brakes. When you are exiting the highway, you often are traveling into a more restricted situation: low visibility curves, lower ramp speed limits, unfamiliar exits. This makes the driver more proactively want to slow down. The driver will brake to a speed where they feel they can control the car. For me this is an automatic response, I don’t “think” to slow down fast.
As others have mentioned, automatic transmissions provide some non-zero force to the wheels, even when the accelerator is not pressed. The only way to counter this force is to apply the brake. As the speed slows, the “impulse” provided by the transmission becomes more of a factor. AT cars will never come to a complete stop until the brakes are applied strongly enough, except perhaps on a steep enough uphill.
Drivers intuitively know how their cars will react as they approach a stop, so they let the car do its thing until the stop is required. They apply the brake to allow the car to stop smoothly, and this takes some muscle memory. Driving someone else’s car will take some getting used to for this reason.
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