Because it is how fast it goes and it depends on the speed
To solve this problem we will apply the principles of conservation of energy, for which we have to preserve the initial kinetic energy as elastic potential energy at the end of the movement. If said equality is maintained then we can affirm that,


Here,
m = mass
k = Spring constant
x = Displacement
v = Velocity
Rearranging to find the velocity,



Our values are,



Replacing our values we have,


Therefore the velocity is 
Answer: 1.5×10^10 N/C
Explanation:
E= F/q
Where E= magnitude of the electric field
F= force of attraction
q= charge of the given body
Given F= 6.5×10^-8 N
q= 4.3× 10^-18 C
Therefore, E = 6.5×10 ^-8/ 4.3×10^-18
E = 1.5×10^10 N/C
Answer:B
Explanation:
Initial velocity, u=0m/s
Distance,s=20m
a=+g=9.8m/s*s
Using v*v=u*u+2gs
v*v=0+2*9.8*20
v*v=392
v=19.8
When s=20m, v = 19.8m/s
Therefore when v = 10m/s, s= 10*20/19.8
s =10.1m