A.
According to the equation: v=λ*f
λ stands for wavelength. wavelength increases, the frequency will decrease. lower frequency deserves low energy.
We use the equation of motion for vertical component,

Here,
is displacement of bullet,
is vertical initial velocity of bullet which is equal to zero because bullet was fired horizontally, and t is time of flight.
Therefore,

Given, 
Substituting the values, we get time of flight

It takes work to push charge through a change of potential.
There's no change of potential along an equipotential path,
so that path doesn't require any work.
Answer:
Explanation:
a = 4ms⁻², Vf = 180 m/s & Vi = 140m/s
a =
4 = 
t = 40/4
t = 10sec
To Measure Distance Use third Equation of Motion:
2aS = Vf²-Vi²
S = 
S = 12800/8 = 1600m