What does hubble's law tell us?
a) the faster a spiral galaxy's rotation speed, the more luminous it is.
b) the longer the period of a cepheid variable, the greater its luminosity.
c) for every force, there is an equal and opposite reaction force.
d) the more distant a galaxy, the faster it is moving away from us. old, red, and bright and have fewer heavy elements.

Hubble's law tell us that the more distant a galaxy, the faster it is moving away from us. old, red, and bright and have fewer heavy elements.

Option D

Explanation:

Hubble's law explains astronomy that galaxies are moving apart and that their rate of speed is proportional to their distance. This leads to the expanding picture of the universe and by extrapolation back to the Big Bang theory.

The dominant movement occur at the universe causes the gentle expansion called Hubble's Law. The Hubble distance would be the distance between the galaxies and the Earth currently traveling from us in the speed of light, as evidenced by the change in Hubble's law in the equation,

Where,

D- galaxy’s distance (Mpc)

H – Hubble constant (km/sec/Mpc)

V- galaxy’s velocity (km/sec)

While galaxies usually change as expanding smooth, distant stars move faster, and other movements cause mild deviations from the lines provided by Hubble's law.

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.