How Much Incline Is Needed For A Typical Loaded Truck To Coast Along AT 60 MPH?

Question

I would also be interested in knowing how much incline is needed for a typical car to coast along at 60 mph. Or a single loaded train car. Or a long loaded train.

Interestingly a good glider only needs a 60 to 1 (1.66 percent) incline to coast along at 60 mph, and thus only requiring 1 lb of steady pull for every 60 lbs it is carrying and at 60 mph). Thus it appears it is difficult for wheel supported machines on a solid surface to carry weight at 60 mph with as little drag as the machine that somehow carries it weight on the squishy air. Very amazing to me. The less drag any transportation machine encounters for every pound it is carrying, the less slope it needs to coast on.

I have learned a good bicycle with a good bicyclist, needs a 13 percent slope to coast along at 60 mph, thus needing 8 times as much slope as the glider needs to coast at that speed. Yet I realize a loaded and streamlined truck does not need near that much incline.

God Bless

Answer 1

It depends on the friction of the road and the air resistance. Without some force holding the truck back, it would keep accelerating even if it was just a gentle slope.

F = ma so a=F/m if there isn't a force counteracting gravity, the truck would just keep accelerating. If the truck has a large frontal area, it will accelerate until the air resistance equals the force of gravity on the incline. That would be the terminal velocity. Same thing for a sky diver. They max out at about 200mph.

If the truck goes 200 mph in freefall and 0 mph for a 0% slope it stands to reason that for 60 mph it would need a 60/200 or 30% slope.