paragraph: Abrasion is another type of weathering. Like ice wedging, it is a form of mechanical weathering. Like ice wedging, abrasion does not change the rock into another type of rock. With abrasion, one rock or piece of sediment bumps against another rock. Rocks dont normally roll around on their own, so why do they move? There are a couple of reasons a rock may move. Gravity can cause rocks to move. They may roll downhill or fall off a cliff. As they roll down a hill, they bump into each other. Maybe a moving rock hits a rock that is not moving at the bottom of the hill. Moving water causes rocks and sediment to move. Rocks are bounced along the bottom and bump against one another. As they collide, they begin to chip away at each other. Angular rocks become more rounded with each collision. Strong winds cause abrasion. The wind carries sediment. This sediment is thrown against other rocky surfaces by the wind. It is like sand-blasting a rock. 
question: How does strong wind cause abrasion?
answer: Moving waters