Answer: 4.27 *10^6 N/C
Explanation: In order to calculate the electric field along the axis of charged ring we have to use the following expression:
E=k*x/(a^2+x^2)^3/2 where a is the ring radius and x the distance to the point measured from the center of the ring.
Replacing the data we have:
E= (9* 10^9* 0.3* 50 * 10^-6)/(0.1^2+0.3^2)^3/2
then
E=4.27 * 10^6 N/C
Answer:
Explanation:
Given
mass of cylinder is M
radius R
velocity of center of mass is v
As there is no slipping therefore cylinder will rotate as well as translate
Moment of inertia of cylinder 
Kinetic Energy of cylinder 
Rotational energy 
for rolling

where 

Total kinetic Energy 
To make sure that we have enough resourses to sustain ourselves. You see, if we use up, say, all water on earth, then obviously we won't have any more and we'll die.
Answer: 50 m/s
Explanation: speed v = 2· pi·n·r = 2· 3.14· 2 s^-1· 4 m