Answer:
F'= 4F/9
Explanation:
Two small objects each with a net charge of +Q exert a force of magnitude F on each other. If r is the distance between them, then the force is given by :
...(1)
Now, if one of the objects with another whose net charge is + 4Q is replaced and also the distance between +Q and +4Q charges is increased 3 times as far apart as they were. New force is given by :
.....(2)
Dividing equation (1) and (2), we get :

Hence, the correct option is (d) i.e. " 4F/9"
<h3>Question:</h3>
How to find g (acceleration due to gravity)
<h3>Solution:</h3>
We know,
Acceleration due to gravity (g)

where, G = Gravitational constant

M = Mass of the earth

R = Radius of the earth

Putting these values of G, M and R in the above formula, we get

So, the value of acceleration due to gravity is

Hope it helps.
Do comment if you have any query.
B) a rock being tossed high into the air
Answer:c
Explanation:
Given
Alice launches with horizontal velocity 
Tom simply drops straight down from the edge
Time taken by both the person is same as they have same initial vertical velocity i.e. zero so the time taken to reach the ground is zero.
Although Alice will travel more horizontal distance compared to Tom.
Thus option c is correct
In the question, you just gave a complete and detailed
description of the plane's velocity vector:
4,000/16 meters/second , heading 35 degrees .
You might want to simplify the speed and make it a unit rate,
but otherwise, it's perfect.
250 meters/second, heading 35 degrees .