Question

Four objects that are symmetrical along vertical planes are placed in four containers in the orientation shown below. Molten wax is poured in each of these containers up to the level indicated on the objects. Assuming that wax does not stick to the objects, which of the objects will leave its \textbf{exact negative impression on the set wax when they are vertically lifted?}

• A. A
• B. B
• C. C
• D. D

Hint:

For casting and impression problems: \begin{itemize} \item Check for undercuts below the casting level, \item Ensure all faces are draft-friendly for vertical removal, \item Symmetry alone does not guarantee removability. \end{itemize}

Answer 1

The Correct Option is A, D

Step 1: For an object to leave an exact negative impression when lifted vertically, it must not have any overhangs or undercuts below the wax level that would obstruct a straight upward removal. \bigskip Step 2: Since all objects are symmetric along vertical planes, check each option for hidden undercuts with respect to the indicated wax level (dashed line). \bigskip Step 3: \begin{itemize} \item A: All surfaces below the wax level taper or extend outward such that the object can be lifted straight up without breaking the wax — valid. \item B: The cylindrical cross-pieces create overhangs below the wax level, preventing clean vertical removal — invalid. \item C: Re-entrant shapes below the wax line cause locking with the wax — invalid. \item Option D: The geometry allows vertical lifting with no undercuts beneath the wax level — valid. \end{itemize} \bigskip Final Answer: \[ \boxed{\text{A, D}} \] \bigskip