Weegy: The principle physical properties of wood are strength, hardness, stiffness and density. Dense types of wood are usually hard and strong. The term strength covers a number of different properties. [ [ Strength varies greatly with seasoning and with the direction of the grain; wood is much stronger when cut along the grain than when cut across it. Toughness is a measure of strength against sudden, repeated stress. Wood is naturally very durable. If not attacked by living things, it can last for hundreds or even for thousands of years. Is there anything else I can assist you with today? ] ] (More)