When we observe a distant galaxy whose photons have traveled for 10 billion years before reaching Earth, we are seeing that galaxy as it was when the universe was:.
a) 10 billion years old.
b) 7 billion years old.
c) 4 billion years old.

a) 10 billion years old.

Explanation:

We see things only when the light from the source hits our eyes. So, if the light which has been received by our eyes has been traveling for 10 billion years then we are actually seeing the galaxy which is 10 billion years old. The galaxy is 10 billion light years away.

Therefore, the answer is a) 10 billion years old.

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.

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.