Let's say that the number density of galaxies in the universe is, on average, 3 × 10–68 galaxies/m3. If astronomers could observe all galaxies out to a distance of 1010 light-years, how many galaxies would they find? (Note that there are 1016 meters in 1 light-year.)

They would find galaxies.

Explanation:

Given that,

The number of density of galaxies in the universe is 3×10⁻⁶⁸ galaxies /m³.

Assuming that, the astronomers are observing at the center of sphere.

So, they can observe the sphere of space whose radius 10¹⁰ light years.

1 light year = 10¹⁶ meters

10¹⁰ light years =10¹⁰ .10¹⁶ meters

                         =10²⁶meters

The volume of the space is

=

m³

m³.

The number of galaxies

= Volume of the space × density

galaxies

= galaxies

They would find galaxies.

he made 11 calls in one day

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.