<span>The correct option is D) both A and B. In fact, the strength of an electric field produced by a single point charge is given by
</span>
<span>
where Q is the charge that generates the field, k is the Coulomb's constante and r is the distance from the charge source of the field.
From the equation, we see that the strength of the field depends on A) the amount of charge that produced the field (Q) and B) the distance from the charge (r), so the correct option is D.</span>
Explanation:
Given: uniform electric field E= 82.0 kN/C.
a) charge density σ =ε_0 E.
therefore, 
b)Total charge on each face = σA
q=σA
Answer:
minimum speed v=
Explanation:
Recall the formula for centripetal force;
Centripetal force is the force that is required to keep an object moving in circular part
where;
F=centripetal force
m=mass of object
r=radius of curvature
v= minimum speed
To find minimum speed make v the subject of formula;
v=
Answer:
Approximately 
if that athlete jumped up at 
. (Assuming that 
.)
Explanation:
The momentum 
of an object is the product of its mass 
and its velocity 
. That is: 
.
Before the jump, the speed of the athlete and the earth would be zero (relative to each other.) That is: 
and 
. Therefore:
and 
.
Assume that there is no force from outside of the earth (and the athlete) acting on the two. Momentum should be conserved at the instant that the athlete jumped up from the earth.
Before the jump, the sum of the momentum of the athlete and the earth was zero. Because momentum is conserved, the sum of the momentum of the two objects after the jump should also be zero. That is:
.
Therefore:
.
.
Rewrite this equation to find an expression for 
, the speed of the earth after the jump:
.
The mass of the athlete needs to be calculated from the weight of this athlete. Assume that the gravitational field strength is 
.
.
Calculate using 
and 
values from the question:
.
The negative sign suggests that the earth would move downwards after the jump. The speed of the motion would be approximately .
Answer:
The electronic transition of an electron back to a lower energy level generates an emission spectrum.
Explanation:
The atomic emission spectrum¹ of an element has its origin when an electronic transition² occurs. An electron in an atom or ion³will absorb energy coming from a source and pass to a higher energy level, the electron, upon returning to its base state will emit a photon⁴ or a series of photons.
Hence, that leads to the formation of an emission spectrum.
Remember that an electron has energy levels in an atom or ion, at which each energy level has a specific value.
The energy values will differ from one element to another. So, it can be concluded that each element has a unique pattern of emission lines.
Key terms:
¹Spectrum: Decomposition of light in its characteristic colors.
²Electronic transition: When an electron passes from one energy level to another, either for the emission or absorption of a photon.
³Ion: An atom electrically charged due to the gain or loss of electrons.
⁴Photon: Elementary particle that constitutes light.
