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?

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

where

m is the mass of the object

g is the acceleration due to gravity

The mass of an object can be rewritten as

where

is the density of the material

V is the volume of the object

So the weight can be rewritten as

For the block of concrete in this problem we have:

is the density of concrete

is the volume of the block

is the acceleration due to gravity

So the weight of the block is:

the reason is because the moon has some form of gravity, and that gravity pulls the ocean tides.

snell's law

refractve index = sin incidence / sin refraction