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"
Answer: D. places where the magnetic field strength is either greater or less than the expected strength.
Explanation:
Magnetic anomaly refers to the change in the magnitude of the magnetic field of the Eatth with respect to the location's expected value.
Magnetic anomalies are places where the magnetic field strength is either greater or less than the expected strength. Therefore, the correct option is D.
When you're talking about gravity, it's easy to identify the equal
opposite forces.
Gravity ALWAYS produces an equal pair of opposite forces.
They both act between the centers of the two objects, one in
each direction.
Consider the equal pair of opposite gravitational forces between
you and the Earth. One force acts on you, and draws you toward
the center of the Earth. We call that force "your weight".
The other one acts on the Earth, and draws it toward the center
of you. Hardly anybody ever talks about that one, but the two
forces are equal ... your weight on Earth is equal to the Earth's
weight on you !
I think by using data collected by Tycho Brahe