The diameter of a Guokui is about_________.

A steel wire with the diameter of d=1mm is wound around a winding drum with the diameter of 2m. Knowing that the allowable stress of the steel wire is [σ] =200MPa, E=200GPa, determine the maximum stress and the largest size of diameter of the steel wire.

The moon is about _____ in diameter as the earth.

The outside diameter of the pipe is （） the diameter of the bore of the piston rod， the result being that an annular space formed between the piston rod and the pipe.

The piston rings are manufactured with a diameter （） the bore of the cylinder.

中国大学MOOC: The diameter of the ping-pong ball is ___.

The meaning of SΦ in dimension is:(Single option: 10 points) A: The symbol of sphere diameter B: The symbol of sphere radius C: The symbol of circle diameter D: None

坐骨棘间径（interspinous diameter）正常值（）

PM 2.5 is a particulate matter with a mean aerodynamic diameter of 2.5 _______.

Exciting conduction velocity of nerve fibers () A: is connected with the square of the diameter B: is connected with the diameter C: has nothing to do with the thickness of myelin sheath D: is unaffected by temperature E: is associated with the intensity of stimulation