steel
It happens because in solids the amplitude of wave is less then other medium therefore distance travelled is less in solids therefore speed is increased.
capillary action phenomenon
Capillary action is the phenomenon by which any liquid rises up in a wick or tube. It is due to surface tension of liquids. The height of rice up of liquid is depend upon surface tension of the water. This is occurs in small plants also.
offer no resistance to the flow of electricity
Superconductor is the property in which 0 resistence obtained at a certain temperature and in a some substance. Ex. Mercury which shows superconductivity phenomena below the temperature 4. 3 k.
vaccum
Light waves are transverse waves they do not require material medium to travel. Hence they are called electromagnetic waves. Light waves travel in vacuum with the velocity 3*10^7 m/s.
necessary centripetal force may be obtained from the horizontal component of the weight of the train
The reason for this to happen is because of the presence of centrifugal force that tends to push the circularly moving object away from the center. The same thing happens when a train is moving at a fast pace over a curve. On a flat track, the train would experience pushing and that can move the center of gravity away. To counter this, the curves are banked in order to get the trains to slightly tilt towards the interior so that the centrifugal force can be countered.