Answer:
a) 17.49 seconds
b) 13.12 seconds
c) 2.99 m/s²
Explanation:
a) Acceleration = a = 1.35 m/s²
Final velocity = v = 85 km/h = 
Initial velocity = u = 0
Equation of motion

Time taken to accelerate to top speed is 17.49 seconds.
b) Acceleration = a = -1.8 m/s²
Initial velocity = u = 23.61\ m/s
Final velocity = v = 0

Time taken to stop the train from top speed is 13.12 seconds
c) Initial velocity = u = 23.61 m/s
Time taken = t = 7.9 s
Final velocity = v = 0

Emergency acceleration is 2.99 m/s² (magnitude)
Answer and Explanation:
The computation of the shortest wavelength in the series is shown below:-

Where
represents wavelength
R represents Rydberg's constant
represents Final energy states
and
represents initial energy states
Now Substitute is

now we will put the values into the above formula


Now we will rewrite the answer in the term of 

So, the whole Paschen series is in the part of the spectrum.
The free electrons in metals can move through the metal, all while receiving and losing electrons, allowing metals to conduct electricity. Example: copper is a great conductor of electric current.