Answer:
Change in electric potential energy ∆E = 365.72 kJ
Explanation:
Electric potential energy can be defined mathematically as:
E = kq1q2/r ....1
k = coulomb's constant = 9.0×10^9 N m^2/C^2
q1 = charge 1 = -2.1C
q2 = charge 2 = -5.0C
∆r = change in distance between the charges
r1 = 420km = 420000m
r2 = 160km = 160000m
From equation 1
∆E = kq1q2 (1/r2 -1/r1) ......2
Substituting the given values
∆E = 9.0×10^9 × -2.1 ×-5.0(1/160000 - 1/420000)
∆E = 94.5 × 10^9 (3.87 × 10^-6) J
∆E = 365.72 × 10^3 J
∆E = 365.72 kJ
Answer: Mechanical waves
Explanation:
Mechanical waves require a medium in order to transport their energy from one location to another. A sound wave is an example of a mechanical wave. Sound waves are incapable of traveling through a vacuum.
Let 
be the average acceleration over the first 2.46 seconds, and 
the average acceleration over the next 6.79 seconds.
At the start, the car has velocity 30.0 m/s, and at the end of the total 9.25 second interval it has velocity 15.2 m/s. Let 
be the velocity of the car after the first 2.46 seconds.
By definition of average acceleration, we have
and we're also told that
(or possibly the other way around; I'll consider that case later). We can solve for in the ratio equation and substitute it into the first average acceleration equation, and in turn we end up with an equation independent of the accelerations:
Now we can solve for . We find that
In the case that the ratio of accelerations is actually
we would instead have
in which case we would get a velocity of
