21 S. An object weighs exactly two grams on an analytical balance that has an ac

Question

21 S. An object weighs exactly two grams on an analytical balance that has an accuracy of ±0.1 mg. How should this weight be recorded? 6. If an unseen cavity is in the metal bar that was used in your density determination, what error would result in the volume measurement, and what would be the effect of this error on the calculated density? 7. If water splashes on the sides of the cylinder when you slide the metal bar down the tilted cylinder, what error would result in the volume measurement, and what would be the effect of this error on the calculated density? ion

Explanation / Answer

5. Balance has an accuracy of 0.1 mg. Means it's least count is 0.1 mg. It can measure differences of upto 0.1 mg accurately. therefore, this weight should be recorded as 2000.0 mg or 2.0000 g. ( as it is exactly 2 g and accurate upto 0.1 mg)

6. Density is calculated as mass/volume of body.

Volume calculation depends on the method which is adopted to find volume. If dimensions of bar are measured and volume found by calculation, then it will neglect the cavity and hence volume will be over-estimated. In this case, calculated density will be under estimated as less than actual.

On the other hand, if volume of bar is calculated using displacement method then actual volume will be measured and effect of cavity will be accounted for. In this case, density calculated is the actual density.

7. If water splashes on the sides, then the volume of the bar will be under estimated equal to the volume of water sticking to sides of cylinder. This will lead to a calculated volume lesser than actual, and as a result, calculated density greater than actual.

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