1.

Assume the density of brass weights to be `8 g cm^(-3)` and that of air to be `0.0012g cm^(-3)`. What fractional error arises from neglecting buoyancy of air in weighing and objecte of density `3.4 g cm^(-1)` on a beam balance?A. `2xx10^(-1)`B. `2xx10^(-2)`C. `2xx10^(-3)`D. `2xx10^(-4)`

Answer» Correct Answer - D
Let `m gwt` be the weight of object in vacuum.
Volume of object = `(m)/(3.4)`
weight of air displaced by object = `m/3.4 xx 0.0012`
Volume of brass weight =` m/8`
weight of air displaced by brass weights
`=m/8 xx 0.0012`
Error=differecne in buouancy
`=0.0012[1/3.4-1/8]`
Fractional error = `(0.0012 xx 4.6)/(3.4xx8) = 2 xx 10^(-4)`.


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