Question

5. A Ping-Pong ball has a diameter of 3.80 cm and average density

of 0.084 0 g/cm3. What force is required to hold it completely

submerged under water?

Answer 1

Given:

$\rho=0.0840\:\rm g/cm^3$

$\rho_w=1.00\:\rm g/cm^3$

$R=1.90\:\rm cm$

$$F=F_b-mg=g\rho_w V-mg=gV(\rho_w-\rho)$$

$$F=9.8*\frac{4}{3}*3.14*1.90^3*(1.00-0.0840)*\frac{1}{1000}\\ =0.258\:\rm N$$