The electric field strength is inversely related to the square of the distance.so the strength of the electric field is given by
Here, 
is constant depend upon medium and its value is 
and q is charge and r is the distance.
Given 
and we know the charge of proton, 
.
Therefore,
Answer:
b) 7.00
Explanation:
N( t ) = -20( t - 5 )²
dN/ dt = -20 x 2 ( t - 5 )
For maximum N ( depth )
dN/dt = 0
- 40 ( t - 5 ) = 0
t = 5
So at 2 + 5 = 7 .00 am depth of water reaches its maximum.
100/2.5 because power=energy/time
you could make a self propelled car all you need is cardboard, wheels, and a balloons or rubber bands
