From the diagram above, the bob of the pendulum has the fastest speed at

A blacksmith heated a metal whose cubic expansivity is 6.3 x 10\(^{-6}\)K\(^{-1}\). The area expansivity is

The ratio of the coefficient of linear expansion of two metals \(\frac{∝_1}{∝_2}\) is 3:4. If, when heated through the same temperature change, the ratio of the increase in length of the two metals, \(\frac{e_1}{e_2}\) is 1:2, the ratio of the original lengths \(\frac{l_1}{l_2}\) is