Question

A wire elongates by $1mm$ when a load $W$ is hung from it. If the wire goes over a pulley and the two weights $W$, each are hung at the two ends, then the elongation of the wire will be:

• A. $0.5mm$
  
• B. $1mm$
  
• C. $2mm$
  
• D. $4mm$
  

Answer 1

Answer: (B)

$1mm$

One of the important concepts in theory regarding stress and strain is that an object which undergoes longitudinal strain under lateral stress is actually under the action of the force from both ends.
The given condition is similar to hanging the load on one end, since the ceiling applies the required reaction force to make the situations similar.