Question

The density of un-set concrete is 2.40 x 10 3 kg/m 3 . When a block with volume 0.0708 m 3 is
submerged in the liquid, a force of 66.7 N is needed to keep it from sinking.
Find the weight of the block?

Answer 1

Answer:

1665 N

Explanation:

The weight of an object is the gravitational force that pulls the object towards the Earth's centre. Its magnitude is given by

$W=mg$

where

m is the mass of the object

g is the acceleration due to gravity

The mass of an object can be rewritten as

$m=\rho V$

where

$\rho$ is the density of the material

V is the volume of the object

So the weight can be rewritten as

$W=\rho V g$

For the block of concrete in this problem we have:

$\rho = 2.40\cdot 10^3 kg /m^3$ is the density of concrete

$V=0.0708 m^3$ is the volume of the block

$g=9.8 m/s^2$is the acceleration due to gravity

So the weight of the block is:

$W=(2.40\cdot 10^3)(0.0708)(9.8)=1665 N$