Question

The iron rim is made slightly smaller than the wooden wheel. The rim is usually heated before fixing into the wooden wheel because on heating the iron rim

• A. expands and fits onto the wooden wheel
• B. contracts and fits onto the wooden wheel
• C. no change in the size takes place
• D. expands first, then on cooling contracts and fits onto the wooden wheel.

Answer 1

The correct option is D

expands first, then on cooling contracts and fits onto the wooden wheel.

Explanation for correct option:

(d) expands first, then on cooling contracts and fits onto the wooden wheel

• The tyre is created significantly smaller in diameter than the wheel. The tyre is then mounted on the wheel after being heated, which causes it to expand.
• The tyre compresses as it cools, creating a snug fit on the wheel.
• Hence this is the correct option.

Explanation for incorrect options:

(a) expands and fits onto the wooden wheel

• The tyre does not compress here, thus not creating a snug fit on the wheel
• Hence this is the correct option.

(b) contracts and fits onto the wooden wheel

• On heating the tyre expands to ensure a snug fit.
• Hence this is the correct option.

(c) No change in the size takes place

• The tyre will expand on heating and contract on cooling.
• Hence this is the correct option.

Hence, the correct option is (d) expands first, then on cooling contracts and fits onto the wooden wheel.