Answer: Ok, first lest see out problem.
It says it's a Long cylindrical charge distribution, So you can ignore the border effects on the ends of the cylinder.
Also by the gauss law we know that E¨*2*pi*r*L = Q/ε0
where Q is the total charge inside our gaussian surface, that will be a cylinder of radius r and heaight L.
So Q= rho*volume= pi*r*r*L*rho
so replacing : E = (1/2)*r*rho/ε0
you may ask, ¿why dont use R on the solution?
since you are calculating the field inside the cylinder, and the charge density is uniform inside of it, you don't see the charge that is outside, and in your calculation actuali doesn't matter how much charge is outside your gaussian surface, so R does not have an effect on the calculation.
R would matter if in the problem they give you the total charge of the cylinder, so when you only have the charge of a smaller r radius cylinder, you will have a relation between r and R that describes how much charge density you are enclosing.
Because one pole of the Earth's axis of rotation (the North one) points
almost exactly toward Polaris.
If Polaris had a pimple or a bump somewhere on its edge, you'd see
the bump rotate around the whole edge, like a clock, once a day. But
the whole star appears to stay in one place, because our axis points to it.
d. Maintain constant velocity
Explanation:
A constant velocity leads to no acceleration.
Acceleration is defined as the change in velocity with time:
Acceleration = 
If there is no change in velocity i.e constant velocity.
At constant velocity, the change in velocity is 0.
If we put zero in the equation above, we will obtain an acceleration value of 0.
Learn more:
Acceleration brainly.com/question/3820012
#learnwithBrainly
Answer:
Gravity is the force by which a planet or other body draws objects toward its center. The force of gravity keeps all of the planets in orbit around the sun.
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