Given:
m(mass of the box)=10 Kg
t(time of impact)=4 sec
u(initial velocity)=0.(as the body is initially at rest).
v(final velocity)=25m/s
Now we know that
v=u+at
Where v is the final velocity
u is the initial velocity
a is the acceleration acting on the body
t is the time of impact
Substituting these values we get
25=0+a x 4
4a=25
a=6.25m/s^2
Now we also know that
F=mxa
F=10 x6.25
F=62.5N
Answer:
The magnitude of the force will decrease
Explanation:
The gravitational force is one of the four fundamental forces of nature. It is an attractive force exerted between every object having mass.
Its magnitude is given by the equation:

where
G is the gravitational constant
m1 is the mass of the first object
m2 is the mass of the second object
r is the separation between the objects
As we see from the equation, the magnitude of the gravitational force is inversely proportional to the square of the distance between the objects:

Therefore, this means that as the distance between two bodies increases, the gravitational force will decrease.
Place the boxes 10cm apart, if they are closer that concentrates the mass of the boxes more