The similarities between physical weathering and chemical weathering are that both of the processes wear away rocks. Physical weathering is the process of breaking down the rock's physical structure into smaller pieces, and it works with mechanical forces like friction and impact. On the other hand, chemical weathering alters or changes the rock's chemical composition that occurs at the molecular level. It is accompanied by exchanging of ions and cations.
Biological weathering usually involves the breaking down of rocks with the help of living things such as plants and animals.
For example, plant roots growing through the rocks resulted in the breaking of the rocks into parts. This process is within the scope of physical weathering. In some cases, plants and animals might release acid-forming chemicals that can result in weathering and thereby contributes to the breaking down of rocks. This can be within the scope of chemical weathering.