A toy with reciprocating movement is shown. As the wheels of the toy rotate, the head is required to reciprocate. If given options are indicative of conversion of rotary to linear motion using a disc located at the centre of the wheel shaft, which option will result in the required movement when the toy is pushed forward? Assume a working spring loaded cam mechanism in the relevant option(s). \quad [This question contains an animated GIF image.]
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For rotary-to-linear conversion:
\begin{itemize}
\item Eccentric cams create reciprocating motion,
\item Spring-loaded followers ensure continuous contact,
\item Central cams without offset do not produce reciprocation.
\end{itemize}
Step 1: The toy moves forward, causing the wheels to rotate continuously in one direction. This rotary motion must be converted into a back-and-forth (reciprocating) motion of the head.
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Step 2: A disc mounted at the centre of the wheel shaft can produce reciprocating motion only if:
\begin{itemize}
\item The contact point with the follower is offset from the centre,
\item A spring-loaded follower maintains continuous contact with the disc,
\item The disc profile allows periodic push and release.
\end{itemize}
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Step 3: Evaluate each option:
\begin{itemize}
\item A: The offset does not allow continuous reciprocation — invalid.
\item B: An eccentrically mounted disc with a spring-loaded follower correctly converts rotary motion into linear reciprocation — valid.
\item C: Irregular toothed profile causes non-uniform motion — invalid.
\item Option D: Central contact produces no effective reciprocation — invalid.
\end{itemize}
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Final Answer:
\[
\boxed{B}
\]
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