Question

A block is connected to a light string attached to the bottom of a large container of water. The tension in the string is 3.0N. The gravitational force from the earth on the block is 5.0N. What is the block’s volume? 

(A) 2.0 × 10⁻⁴m

(B) 3.0 × 10⁻⁴m³

(C) 5.0 × 10⁻⁴m³

(D) 8.0 × 10⁻⁴m³

(E) 1.0 ×10⁻³m³

Answer 1

Correct option (D) 8.0 × 10⁻⁴m³

Three forces act on the block, F_t down, mg down and F_b up. F_net = 0 F_b – F_t – mg = 0 F_b – 3 – 5 = 0 

F_b = 8 N – weight of displaced water = ρ_h20 V_dispg 

8 = (1000)V (10) → V = 0.0008m