Gravitational 54411

How much force do we lift a stone in the water that weighs 30 kg and has a density of 2500 kg/m³? Gravitational acceleration g = 10 m/s².

Correct answer:

F =  180 N

Step-by-step explanation:

$$\begin{gathered} m=30\text{kg} \\ \rho =2500{\text{kg/m}}^3 \\ {\rho }_2=1000{\text{kg/m}}^3 \\ g=10{\text{m/s}}^2 \\ V=m/\rho =30/2500=\frac{3}{250}=0.012{\text{m}}^3 \\ {m}_2={\rho }_2\cdot V=1000\cdot 0.012=12\text{kg} \\ {F}_1=m\cdot g=30\cdot 10=300\text{N} \\ {F}_2=m_2\cdot g=12\cdot 10=120\text{N} \\ F=F_1-F_2=300-120=180\text{N} \end{gathered}$$

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