Question

In bullock carts, the iron rim is usually heated before fixing it to the wooden wheels. This is because after heating iron ___

• A. contracts and fits to the wooden wheel
• B. expands and fits to the wooden wheel
• C. first expands and then contracts, thus fitting to the wooden wheel
• D. none of these

Answer 1

The correct option is C

first expands and then contracts, thus fitting to the wooden wheel

The iron rim is usually smaller than the wooden wheel of the bullock cart. How does it fit so perfectly then?

The secret is the expansion of metals on heating. Iron is a metal which expands on heating. The iron rim is heating so that it expands and its size increases. This allows wooden wheel to fit in. Then as the rim cools down, it contracts and becomes smaller. Now it firmly holds on to the wheel.