JAMB Physics 2024 Paper

Concept:Upthrust is the buoyant force exerted by a fluid on a fully immersed object. It equals the weight of the fluid displaced by the object.Explanation:When the spherical ball is totally immersed, the upthrust $U$ is given by the product of the volume $V$ of the ball, the density $\rho$ of the liquid, and acceleration due to gravity $g$.Thus, $U = V \rho g$.Substitute the values: $V = 4.2 \times 10^{-4}\ \mathrm{m^3}$, $\rho = 1028\ \mathrm{kg\,m^{-3}}$, and take $g = 10\ \mathrm{m\,s^{-2}}$.$U = (4.2 \times 10^{-4}) \times 1028 \times 10$.$U = 4.2 \times 1028 \times 10^{-3}$.Since $1028 \times 10^{-3} = 1.028$, we get $U = 4.2 \times 1.028 = 4.3176\ \mathrm{N}$.Rounding to one decimal place gives $U \approx 4.3\ \mathrm{N}$.Answer:The upthrust on the ball is approximately $4.3\ \mathrm{N}$, so the correct option is B.