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Methods of Separation of Substances - Threshing

Grade 6CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Threshing is the process used to separate the grain from the stalks after harvesting.

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The process involves beating the dried stalks to free the grain seeds from the chaff.

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Manual Threshing: Involves holding a bundle of stalks and hitting them against a hard surface.

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Animal-assisted Threshing: Bullocks are sometimes used to trample the stalks to separate the grains.

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Mechanical Threshing: For large quantities of grain, machines called 'Threshers' are used to speed up the process.

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Threshing is necessary because the size of the grain is too small and the quantity is too large to be separated by handpicking.

📐Formulae

Total Harvested Mass=Mass of Grains+Mass of Stalks\text{Total Harvested Mass} = \text{Mass of Grains} + \text{Mass of Stalks}

Efficiency of Threshing=Mass of separated grainsTotal mass of grains in stalk×100\text{Efficiency of Threshing} = \frac{\text{Mass of separated grains}}{\text{Total mass of grains in stalk}} \times 100

💡Examples

Problem 1:

A farmer harvested a bundle of wheat weighing 65 kg65\text{ kg}. After threshing, he collected 52 kg52\text{ kg} of stalks (chaff). Calculate the mass of the wheat grains obtained using the conservation of mass principle.

Solution:

65 kg−52 kg=13 kg65\text{ kg} - 52\text{ kg} = 13\text{ kg}

Explanation:

Using the relationship Mass of Grains=Total Mass−Mass of Stalks\text{Mass of Grains} = \text{Total Mass} - \text{Mass of Stalks}, we perform the subtraction: 65−5213\begin{array}{r} 65 \\ - 52 \\ \hline 13 \end{array} Thus, the mass of the wheat grains is 13 kg13\text{ kg}.

Problem 2:

Why is threshing preferred over handpicking for separating grains like paddy or wheat?

Solution:

Grains are much smaller than fruits (like mangoes) and are present in thousands on a single stalk.

Explanation:

Because the number of grains is very high and their size is small, picking them by hand from the stalks is practically impossible. Therefore, mechanical or manual beating (threshing) is used to separate them efficiently.