# A 3-kg plastic tank that has a volume

A 3-kg plastic tank that has a volume of $0.2\,\text{m}^3$ is filled with liquid water. Assuming the density of water is 1000 kg/$\text{m}^2$, determine the weight of the combined system.

#### Solution:

We know that the density of water is 1000 kg/$\text{m}^2$. We can use the following equation to figure out the weight of the combined system.

$m=\rho V$

(Where m is mass, $\rho$ is density, and V is volume)

Substitute the values we know:

$m=\rho V$

$m=(1000)(0.2)$

$m=200$ kg

The combined mass is the mass of the tank plus the water.

$m_{total}=3+200$

$m_{total}=203$ kg

The weight can then be calculated using the following equation:

$W=mg$

(Where W is weight, m is mass and g is force of gravity)

Substitute the values we know:

$W=mg$

$W=(203)(9.81)$

$W=1991.43$ N

$W=1991.43$ N