Where does gravity come from? How does an object's mass shape the fabric of
spacetime?

gravity comes from all its mass. All its mass makes a combined gravitational pull on all the mass in your body. That's what gives you weight.

Every object in the universe pulls on the space around it, drawing the fabric of space-time toward its center. The more massive the object, the more it pulls. ... The physicist John Wheeler captured these odd notions

the speed increase from w to x due to increased gravity force

the speed decreases from x to y due to decrease in gravity

that would be called plucking : )

explanation:

''plucking, also referred to as quarrying, is a glacial phenomenon that is responsible for the erosion and transportation of individual pieces of bedrock, especially large "joint blocks". as a glacier moves down a valley, friction causes the basal ice of the glacier to melt and infiltrate joints (cracks) in the bedrock."