Does this advice apply to all cars?
In: 156
As to your second question: No. Some cars are designed amazingly well to go really really fast really really quickly and some actual regain mileage from braking just right and not gradually (EV or hybrid).
As to your first question:
Inertia.
The ELi5 is that mass doesn’t want to change what it’s doing.
If it’s at rest it doesn’t want to start moving.
If it’s moving it doesn’t want to stop.
It’s reasonably instinctual when you just push things around but you can very easily measure it.
Without going into the math inertia fights you harder the more change you want to impart.
Pushing a marble to go 1 kph in 1 sec across a table takes a tenny tiny amount of energy.
pushing that marble to go 100kph across a table takes more then 100 times the same energy.
In the same way a baseball thrown at you at 10 kph will hurt but one at 20kph will hurt more than twice as much.
If you think about accelerating a car a series of small steps for each kph then using the previous analogy if you make the steps longer inertia doesn’t fight you as hard for every step and you use less energy.
With braking most cars actually don’t car BUT if you time it just right you can roll until the light turns green and you can then start moving again without coming to a stop. That saves you a bit of energy since you don’t fight inertia from 0 kph.
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