Question

33. A weight of 450 g produces an extension of 3.5 cm in a elastic string, find
(a) how much weight is required to produce an extension 1.75 cm.
(b) how much extension will be produced by 9 kg weight.
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Answer 1

Answer:

a) 450/2 = 222.5 g

b) The extension by 1 g = 3.5 cm /450g = 0.008

9 kg = 9×1000g = 9000g

so extension by 9000g = 9000g × 0.008 = 72cm

Answer 2

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Given us the stress and strain as 450 g and 3.5 cm respectively.

So, Let's find the modulus of elasticity first,

⇒ Stress = k × Strain

⇒ k = 450 / 3.5

⇒ k = 128.57 g/cm

Now, In the second case, we have

Strain = 1.75 cm

k = 128.57 g/cm

We have to find, stress, Similarly

⇒ Stress = k × Strain

⇒ Stress = 128.57 × 1.75

⇒ Stress = 224.99

⇒ Stress ≈ 225 g

So, The required weight is 225 g