The area of square is increasing with the rate of 144 cm/s2.
For physics, The term "thermal expansion" refers to a material's change in length, width, height, or volume when its temperature is raised or lowered. Solids exhibit particularly noticeable thermal expansion due to their closely packed atoms. There are numerous uses for thermal expansion of solids in daily life.
A solid's atoms vibrate more quickly around their fixed positions when it is heated. As a result, there is little relative growth in the size of solids during heating. In order to prevent buckling when exposed to heat from the sun, metal train tracks feature tiny gaps.
L = length of a side
A = L2
dA/dt = 2L dL/dt
dL/dt = 8 cm/s
A = 81 cm2 ⇒ L = √A = √81 cm = 9 cm
dA/dt = 2(9cm)(8 cm/s) = 144 cm/s2
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