Answer:
a.18.5 m/s
b.1.98 s
Explanation:
We are given that
a.Let 
be the initial velocity of the ball.
Distance,x=30 m
Height,h=1.8 m
Substitute the values
Initial velocity of the ball=18.5 m/s
b.Substitute the value then we get
t=1.98 s
Hence, the time for the ball to reach the target=1.98 s
Answer:
Explanation:
The unknown charge can not remain in between the charge given because force on the middle charge will act in the same direction due to both the remaining charges.
So the unknown charge is somewhere on negative side of x axis . Its charge will be negative . Let it be - Q and let it be at distance - x on x axis.
force on it due to rest of the charges will be equal and opposite so
k3q Q / x² =k 8q Q / (L+x)²
8x² = 3 (L+x)²
2√2 x = √3 (L+x)
2√2 x - √3 x = √3 L
x(2√2 - √3 ) = √3 L
x = √3 L / (2√2 - √3 )
Let us consider the balancing force on 3q
force on it due to -Q and -8q will be equal
kQ . 3q / x² = k3q 8q / L²
Q = 8q (x² / L²)
so charge required = - 8q (x² / L²)
and its distance from x on negative x side = √3 L / (2√2 - √3 )
The kinetic energy would be 53,775J:)
