Electricity which may efficient transportation if you develop your way depending contact metal basis , such as electric train . 
-Water is from of heat-energy using solar power which run a turbine may be wheel on a railway path.
        
             
        
        
        
Answer:
the speed of light in air is about 299,000,000 and 3×10⁸ m/s
 
        
                    
             
        
        
        
Explanation:
Given that,
Length of gold wire, l = 4 m
Voltage of battery, V = 1.5 V
Current, I = 4 mA
The resistivity of gold, 
Resistance in terms of resistivity is given by :

Also, V = IR
So,

A is area of wire, 
 , r is radius, r = d/2 (diameter=d)
, r is radius, r = d/2 (diameter=d)

Out of four option, near option is (C) 17 μm.
 
        
             
        
        
        
Answer:
On a roller coaster, energy changes from potential to kinetic and back again many times over and over the course of the ride. Kinetic energy is energy that an object has because of its motion. All moving objects possess kinetic energy, which is determined by the mass and speed of the object.
Explanation: