An iron rocket fragment initially at - 100 ° C enters the earth's atmosphere almost horizontally and quickly fuses completely in atmospheric friction. Specific heat of iron is 0. 11kcal kg ^ - 1 ° C^ - 1 , its melting

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Correct answer: B. 1. 32kms^ - 1 &

The kinetic energy of the fragment is changed to heat. Expressing mass m in kilograms everywher, we have

\dfrac{1}{2}mv^{2} = \left[m\left(30\right) + m\left(\text{0.11}\right)\left(153{5}^{∘} + 10{0}^{∘}\right)\right]4184

v^{2} = \left(8368\right)\left[30 + 180\right] ≃ \text{1.76} \times 1{0}^{6}

Hence

v = \left(\sqrt{\text{1.76}}\right) \times 1{0}^{3} = {1.32 km s}^{- 1}

An iron rocket fragment initially at - 100 ° C enters the earth's...

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