Answer to Question #11721 in Mechanics | Relativity for Michelle

Question

A 100g cube 2cm on each side is attached to a string and then totally submerged in water. What is the buoyant force, and what is the tension in the rope? I found the buoyant force, but I don't know how to find the tension in the rope. If you could help me that would be amazing. Thank you so much.

Answer 1

A 100g cube 2cm on each side is attached to a string and then totally submerged in water. What is the buoyant force, and what is the tension in the rope? I found the buoyant force, but I don't know how to find the tension in the rope.

V = (0.02m)³ = 8·10^(-6) m³;
m = 0.1 kg

So, the buoyant force is

Fb = pgV = (1000 kg/m³)(9.8 m/s²)(8·10^(-6) m³) ≈ 0.0784 N

The sum of all forces acting along y-axis is equal to zero:

T + Fb - mg = 0
T = mg - Fb

So, tension of a rope is

T = (0.1 kg)(9.8 m/s²) - 0.0784 N = 0.980 N - 0.0784 N = 0.902 N.