1.  In a mechanical wristwatch, which part works in the same way
   as a pendulum in a clock?
2.  The discovery of which principle made the accurate measurement
   of time possible? What is this principle? Explain with a diagram.

Solution & Explanation

Answer to Q1

In a mechanical wristwatch, the balance wheel (often combined
with a spiral hairspring) functions similarly to a pendulum in a traditional clock.
Just as a pendulum swings back and forth at a consistent rate, the balance wheel
oscillates in a regular motion. This regularity is essential for keeping accurate time.

Answer to Q2

The principle that made the accurate measurement of time possible was the discovery
of the isochronism of a pendulum, famously explored by Galileo.
Isochronism refers to the property that the time period of a pendulum’s swing
remains nearly constant regardless of its amplitude (for small oscillations).

This principle led to more precise timekeeping devices. Clockmakers later adapted
the idea using escapements and balance springs in watches
so that even small pendulum-like oscillations could be used to measure time accurately.

Note: A schematic diagram of a pendulum or balance wheel escapement
would typically show how the swinging or oscillating component is anchored at a pivot
point, allowing it to move back and forth and “tick” at regular intervals.
(Diagram not shown here.)