First slide

Fluid statics

Question

Assume the density of brass weights to be 8 g ${cm}^{- 3}$ and that of air to be 0.0012 g ${cm}^{- 3}$ . What fractional error arises from neglecting buoyancy of air in weighing and object of density 3.4 g ${cm}^{- l}$ on a beam balance?

Easy

A

$2 \times 10^{- 1}$
B

$2 \times 10^{- 2}$
C

$2 \times 10^{- 3}$
D

$2 \times 10^{- 4}$

Solution

Let m gwt the weight of object in vaccum.
Volume of object = $\frac{m}{3.4}$
Weight of air displaced by object = $\frac{m}{3.4} \times 0.0012$
Volume of brass weight = $\frac{m}{8}$
Weight of air displaced by brass weighs = $\frac{m}{8} \times 0.0012$
Error = difference in buoyance
= m0.0012[ $\frac{1}{3.4} - \frac{1}{8}$ ]
Fractional error = $\frac{0.0012 \times 4.6}{3.4 \times 8} = 2 \times 10^{- 4}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App