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2 answers:
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Answer:
<em>The speed of the projectile when it impacts the ground is 1000 m/s</em>
Explanation:
<u>Vertical Launch</u>
When an object is launched vertically and upwards it starts to move at an initial speed vo, then the acceleration of gravity makes that speed to reduce until it reaches 0. The object has reached its maximum height. Then, it starts to move downwards in free fall, with initial speed zero and gradually increasing it until it reaches the ground level. We will demonstrate that the speed it has when impacts the ground is the same (and opposite) as the initial speed vo.
The speed when the object is moving upwards is given by
The time it takes to reach the maximum height is when vf=0, i.e.
solving for t
The maximum height reached is
Then, the object starts to fall. The object's height is given by
where t' is the time the object has traveled downwards. The height will be 0 again when
Solving for t'
We can see the time it takes to reach the maximum height is the same it takes to return to ground level. Of course, the speed when it happens is
Thus, the speed of the projectile when it impacts the ground is 1000 m/s
The question is missing, however, I guess the problem is asking for the value of the force acting between the two balls.
The Coulomb force between the two balls is:
where
is the Coulomb's constant, 
is the intensity of the two charges, and 
is the distance between them.
Substituting these numbers into the equation, we get
The force is repulsive, because the charges have same sign and so they repel each other.
The Coulomb force between the two balls is:
where
Substituting these numbers into the equation, we get
The force is repulsive, because the charges have same sign and so they repel each other.