Question

The wind displacement force F = 180 N acts on the sailing ship, and the water resistance force f = 160 N, which impedes its movement. (figure 4.22). Calculate the mass of the ship, knowing that along the way 120 m its speed increased from 1.5 m / s to 2.8 m / s.

Answer 1

According to the Second Newton's Low

$F=ma\to F-F_f=ma\to F-F_f=m\frac{v^2-v_0^2}{2s}$

$m=\frac{2s(F-F_f)}{v^2-v_0^2}=\frac{2\cdot 120\cdot (180-160)}{2.8^2-1.5^2}=859(kg)$