Final answer:
The hole in a heated metal disc becomes larger due to thermal expansion, which causes all parts of the material to expand, including around the hole. This concept has practical applications in fields such as engineering and manufacturing.
Step-by-step explanation:
When a metal disc with a hole is heated, the size of the hole will increase. This is due to the phenomenon known as thermal expansion, where objects expand in all dimensions as temperature rises. Metal, like any other solid, has atoms that move further apart when heated, leading to an expansion of the material in all directions, including the areas around the hole. It's helpful to imagine the metal disc as if the piece removed to make the hole were still there; as the surrounding metal expands, the 'missing piece' would also get larger, hence the hole must become larger too.
This concept also has practical applications in engineering, like ensuring a tight fit between a metal peg and a hole in a block of metal, or preventing thermal stress between different materials with varying expansion coefficients. For instance, when fitting a metal peg into a hole for a snug fit, the hole should be at a higher temperature than the peg during insertion to accommodate the size difference caused by expansion.