How does the strong nuclear force compare with the electrostatic force in the nucleus of an atom?

a. the strong nuclear force is stronger and is only attractive.
b. the strong nuclear force is weaker and acts over longer distances.
c. the strong nuclear force is stronger and acts over longer distances.
d. the strong nuclear force is weaker and is only attractive.

Athin electrical heater is inserted between a long circular rod and a concentric tube with inner and outer radii of 20 and 40 mm. the rod (a) has a thermal conductivity of ka = 0.15 w/(m*k), while the tube (b) has a thermal conductivity of kb = 0.8 w/(m*k) and its outer surface is subjected to convection with a fluid of temperature t= -15°c and heat transfer coefficient 60 w/(m2 *k). the thermal contact resistance between the cylinder surfaces and the heater is negligible. (a) determine the electrical power per unit length of the cylinders (w/m) that is required to maintain the outer surface of cylinder b at 15°c. (b) what is the temperature at the center of cylinder a?