See coulomb's law. Force is inversely proportional to the distance squared. So if you multiply r by 2, the force is multiplied by (½)² = ¼.
a. F/4
The image produced is magnified and real.
Answer:

Explanation:
given,
s = 400- 16 t²
we know,
Velocity of an object is defined as the change in displacement per unit change in time.
velocity an also be return as




Hence, instantaneous velocity function given by 
To calculate instantaneous velocity, you need to insert value of time.
ex, instantaneous velocity at t = 4 s
v = -32 x 4 = -128 m/s.
Momentum (p) = mass × velocity
P= 200,000×4.5
P= 900,000 .... answer !!