''Rockets travel at 18.5K Miles per hour to leave Earth ( With People INside)'' And your point is?
If they can't understand gravity, they probably won't understand acceleration either. :/
Speeding up is acceleration, slowing down is acceleration and, rotation is acceleration. Traveling at a constant speed is NOT acceleration.
Gravity is a fictitious force that misappropriates actions caused ultimately by electrical forces (Coulombs Law) in order to support the heliocentric argument, an idea that falls apart with basic scientific and logical criticism. The Earth is stationary, neither accelerating nor traveling at a constant velocity.