Question

A cubical block of edge $2cm$ is dipped in water completely, the upthrust acting on the cube is ($g=10m/s^2$)

• A. $240000N$
• B. $240N$
• C. $2.4N$
• D. $0.24N$

Answer 1

The correct option is D

$0.24N$

Step 1: Given data

1. The buoyant force acting on an object submerged in a liquid is $F=\rho gV$
2. Here,$\rho$ is the density of the liquid (here it is water so $\rho =1000Kg/m^3$)
   $g$ is the acceleration due to gravity and
   $V$ is the volume of the submerged object or displaced liquid ($=\frac{mass}{volume}$)

Step 2: Calculating volume of cube

1. length of cube is, $l=2cm$
2. we know that, $volumeofcube={\left(edge\right)}^3$
3. Thus, $V={(2cm)}^3=8c{m}^3$
4. Also, $1cm={10}^{-2}m$
5. So, $V=8c{m}^3=8\times {10}^{-6}{m}^3$

Step 3: Calculating buoyant force

1. $F=\rho gV=1000\times 10\times 8\times {10}^{-6}=0.08N$
2. Thus, the buoyant force will be $F=0.08N$.

Hence, option (D) is correct.