Mechanical weathering is another name for physical weathering. Physical weathering is the breakdown of rocks into smaller particles either by, wind, water, or ice, and in some cases, gravity. 

Mechanical erosion is not a form of erosion. Mechanical weathering breaks down the rock. Erosion is the carrying-away of the broken down rock. mechanical weathering is beating the rock into smaller pieces and chemical weathering is a rock that has been oxidized by iron and changed to a red color where the actual composition of the rock is altered.