Explanation:
i really didn't understand the question
im soo so sorry
Answer : 
Explanation :
Given that
Radius of sphere 
The distance between the centers of the two spheres is

The charge of the sphere 
The magnitude of the repulsive force between the charges pushing them a part is
Using coulomb law




Hence, this is the required solution.
Answer:
2.47 m/s
Explanation:
Momentum = Mass X Velocity
If they were locked together, it means its a perfectly inelastic collision. Therefore,
Total momentum before = Total momentum after
Total momentum before = (20 X 20) - (18 X 17)
= 94
Total momentum after = 94
Y = Object speed after collision
94 = (20+18)Y
Y = 2.47368421 m/s
Sound level at distance of 15 m is given as 20 dB
so intensity at this distance is given as



now if we move closer to some some distance the sound level is now 50 dB
now the intensity is given as



now we know that



so now the distance from friend must be 47 cm