In aeronautics, a propeller, also called an airscrew, converts rotary motion from an engine or other power source into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached several radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis. The blade pitch may be fixed, manually variable to a few set positions, or of the automatically variable "constant-speed" type.
Answer: positive
Explanation: according to newton's second law of motion, the applied force (pull) will produce a motion for the box defined by the formulae
f = ma, where m is the mass of the box and a is the acceleration.
But due to friction, a force of the same magnitude but opposite in direction to the push is applied, hence we have that
f - fr = ma
Where fr is the frictional force.
As we can see from the formulae, f (push) is responsible for a positive work while fr (friction) will bring about a negative work done.
The correct answer is 4 cm :)
A trait shared by dolphins and bats that possibly led to the evolution of echolocation in these two animal groups will be the need to move quickly through dark environments.
<h3>What is the evolution of echolocation?</h3>
Our understanding of the evolution of echolocation in bats has shifted as a result of recent molecular phylogenies. These phylogenies imply that bats with advanced echolocation
According to one interpretation of these trees, laryngeal echolocation originated in the ancestor of all living bats. Echolocation may have been lost in Old World fruit bats
The vast adaptive radiation in echolocation call design is substantially controlled by ecology, demonstrating how environmental perceptual problems influence call design.
A trait shared by dolphins and bats that possibly led to the evolution of echolocation in these two animal groups will be the need to move quickly through dark environments.
Hence option A is correct.
To learn more about the evolution of echolocation refer to the link;
brainly.com/question/20789287
