Question

The extension in an elastic string varies directly as the weight hung on it. If a weight of 150 g produces an extension of 2.8 cm, what weight would produce an extension of 19.6 cm?

Answer 1

Weight that would produce an extension of 2.8 cm = 150 g

Weight that would produce an extension of 1 cm = $\frac{150}{2.8}$ g

Weight that would produce an extension of 19.6 cm = $\frac{150}{2.8}$$\times$19.6 = 1050 g = 1 kg 50 g [1 kg = 1000 g]

∴ A weight of 1 kg 50 g would produce an extension of 19.6 cm.