<span>Density is a measure of an object's </span>mass per unit of volume
Which means that it shows how much mass is contained within a volume of something.
(a) 0.448
The gravitational potential energy of a satellite in orbit is given by:

where
G is the gravitational constant
M is the Earth's mass
m is the satellite's mass
r is the distance of the satellite from the Earth's centre, which is sum of the Earth's radius (R) and the altitude of the satellite (h):
r = R + h
We can therefore write the ratio between the potentially energy of satellite B to that of satellite A as

and so, substituting:

We find

(b) 0.448
The kinetic energy of a satellite in orbit around the Earth is given by

So, the ratio between the two kinetic energies is

Which is exactly identical to the ratio of the potential energies. Therefore, this ratio is also equal to 0.448.
(c) B
The total energy of a satellite is given by the sum of the potential energy and the kinetic energy:

For satellite A, we have

For satellite B, we have

So, satellite B has the greater total energy (since the energy is negative).
(d) 
The difference between the energy of the two satellites is:

An apple falling to the ground is not an example of centripetal acceleration.
The victim's head is accelerated faster and harder than the
torso when the victom is involved in a typical rear-end collision.
The traffic accident where a vehicle crashes into another
vehicle that is directly in front of it is called a rear-end collision.
One of the most common accident in the United States is the
rear-end collision, and in a lot of cases, rear-end collisions are prompted by
drivers who are inattentive, unfavorable conditions of the road, and poor
following distance.
<span>An enough room in front of your car so you can stop when the
car in front of you stops suddenly is one basic driving rule. The person isn’t
driving safely if he / she is behind you and couldn’t stop.</span>