Question

An object moving in a liquid experiences a linear drag force: D⃗ =(bv, direction opposite the motion), where b is a constant called the drag coefficient. For a sphere of radius R, the drag constant can be computed as b=6πηR, where η is the viscosity of the liquid.

Water at 20 ∘C has viscosity η=1.0×10−3Ns/m2. Suppose a 4.4-cm-diameter, 34 g ball is shot horizontally into a tank of 20 ∘C water. How long will it take for the horizontal speed to decrease to 50% of its initial value?

Answer 1