Efficiency of a propeller is defined as the ratio of available power to the engine power which is. . (3). Note, that this definition for efficiency contains the velocity v, which means, that the efficiency approaches zero as the flight speed goes to zero, because the thrust cannot become infinitely large. So this definition is not useful for the special case of static thrust.
1 Compound Fracture: A compound fracture is a fracture in which the injured bone sticks through the skin. 2  Also known as an open fracture, a compound fracture can be a bit more serious in nature.
There are two types of fractures: open and closed. In an open fracture, the ends of the broken bone tear the skin. When the bone and skin are exposed, they are at risk of infection. This type of fracture is also called a compound fracture. In a closed fracture, the broken bone does not break the skin. This type of fracture is also called a simple fracture. But these fractures can be just as dangerous as open fractures.