Black hole, it sucks in pretty much everything in its path
Answer: The electric field is: a) r<a , E0=; b) a<r<b E=ρ (r-a)/εo;
c) r>b E=ρ b (b-a)/r*εo
Explanation: In order to solve this problem we have to use the Gaussian law in diffrengios regions.
As we know,
∫E.dr= Qinside/εo
For r<a --->Qinside=0 then E=0
for a<r<b er have
E*2π*r*L= Q inside/εo in this case Qinside= ρ.Vol=ρ*2*π*r*(r-a)*L
E*2π*r*L =ρ*2*π*r* (r-a)*L/εo
E=ρ*(r-a)/εo
Finally for r>b
E*2π*r*L =ρ*2*π*b* (b-a)*L/εo
E=ρ*b* (b-a)*/r*εo
Answer:
The statement is true: velocity and acceleration have opposite directions in the interval of braking.
Explanation:
Let's say we have a velocity 
.
The acceleration 
is the rate of change of the velocity 
. This means that if is <em>increasing during</em> time, then must be positive. But if is <em>decreasing over</em> time, then will be negative (even though the velocity is positive).
Mathematically:
decreases ⇒
⇒
.
Example:
You could put ice, put it on wheels!
