Solved: PHYSICS Question for NEET

NEET PHYSICSMedium

The velocity of a small ball of mass $M$ and density $d$ , when dropped in a container filled with glycerine becomes constant after some time. If the density of glycerine is $\frac{d}{2}$ , then the viscous force acting on the ball will be

$\frac{Mg}{2}$

$Mg$

$\frac{3}{2}Mg$

$2Mg$

Step-by-Step Solution

When the velocity is constant, the net force is zero. The forces acting are gravity ( $Mg$ downwards), buoyant force ( $F_B$ upwards), and viscous force ( $F_v$ upwards). So, $Mg = F_B + F_v$ . The buoyant force $F_B = V \rho_{liquid} g = V (d/2) g$ . Since $M = Vd$ , $V = M/d$ . Thus $F_B = (M/d) *(d/2)* g = Mg/2$ . Therefore, $F_v = Mg - F_B = Mg - Mg/2 = Mg/2$ .

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