Answer:
The efficiency of a screw is low because of friction.
Explanation:
A screw is a simple machine that is used to convert a torque to linear force and rotational motion to linear motion. The efficiency of a screw is given by :
[tex]\eta=\dfrac{Fl}{2\pi T}[/tex]
Where
l = pitch distance in mm
T = torque in N-m
The efficiency of screw is less because the output is less as compared to input or there is more input than output. This implies that there is more friction.
Hence, the correct option is (b) "friction".
