Answer:
The height of the cliff is 90.60 meters.
Explanation:
It is given that,
Initial horizontal speed of the stone, u = 10 m/s
Initial vertical speed of the stone, u' = 0 (as there is no motion in vertical direction)
The time taken by the stone from the top of the cliff to the bottom to be 4.3 s, t = 4.3 s
Let h is the height of the cliff. Using the second equation of motion in vertical direction to find it. It is given by :



h = 90.60 meters
So, the height of the cliff is 90.60 meters. Hence, this is the required solution.
The magnitude of the source charge is 3 μC which generates 4286 N/C of the electric field. Option B is correct.
What does Gauss Law state?
It states that the electric flux across any closed surface is directly proportional to the net electric charge enclosed by the surface.

Where,
= electric force = 4286 N/C
= Coulomb constant = 
= charges = ?
= distance of separation = 2.5 m
Put the values in the formula,

Therefore, the magnitude of the source charge is 3 μC.
Learn more about Gauss's law:
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