A blacksmith heated a metal whose cubic expansivity is 6.3 x 10\(^{-6}\)K\(^{-1}\). The area expansivity is
A
2.0 x 10-6K-1
B
2.1 x 10-6K-1
C
4.2 x 10-6K-1
D
6.3 x 10-6K-1
Verified Correct Answer: C.
Physical Principles & Numerical Solution
If the linear expansivity = ∝
=> area expansivity \beta = 2∝.
And cubic expansivity δ = 3∝.
=> 6.3 x 10\(^{-6}\) = 3∝
∴ ∝ = \(\frac{6.3 \times 10^{-11}}{3}\) = 2.1 x 10\(^{-6}\)
∴ Area = 2∝ = 2 x 2.1x10\(^{-6}\)
= 4.2 x 10\(^{-6}\)K\(^{-1}\)
Source: WAEC / JAMB / NECO Classroom Archive (Record #14385)