Question

When you put a metal key into its metal lock, you find the key is too tight. Which of the following methods will you adopt to make the key fit properly?
(a) Heat the key and the lock.
(b) Cool the key and heat the lock.
(c) Heat the key and cool the lock.
(d) Cool the key and the lock.

Answer 1

(b) Cool the key and heat the lock.
Key contracts on cooling; similarly, lock expands on heating. This will make the key fit properly in the lock.