Which of these is a wheel & axle?
A.
Doorknob
B.
Hammer
C.
Nail
D.
Oar
A. Doorknob
The correct answer is A. Doorknob.
To determine which of these items is a wheel and axle, we need to understand the characteristics of a wheel and axle. A wheel and axle is a simple machine that consists of a circular object (wheel) attached to a smaller cylindrical object (axle) that rotates through its center. By examining the features of each item, we can identify which one fits this description.
Let's analyze each option:
A. Doorknob: A doorknob does not have a wheel and axle design. It typically consists of a handle mounted on a spindle, which allows the door to be opened or closed by rotating the handle.
B. Hammer: A hammer is not a wheel and axle. It is a hand tool consisting of a heavy head attached to a handle. While it has a cylindrical handle, it does not feature a circular object rotating around it.
C. Nail: A nail is not a wheel and axle. It is a slender, pointed metal object used to fasten materials together.
D. Oar: An oar is indeed a wheel and axle. It is a long, narrow blade that is fixed to a central rod (the axle). The person uses one end of the oar as a lever to rotate the blade (the wheel) in the water, propelling a boat forward.
Therefore, out of the options provided, the oar (option D) is the item that represents a wheel and axle.