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The force of seat acting on the child is a reaction the force of child pressing down on the seat. This is the third Newton's law. The force of a child pressing down the seat and the force of the seat pushing up on the child are the same.
There two forces acting on the child. The first one is the gravitational force and the second one is centrifugal force. In this example, the force of gravity is always pulling down, but centrifugal force always acts away from the center of circular motion.
Part AFor point A we have:

In this case, the forces are aligned, centrifugal is pointing up and gravitational is pulling down.
Part BAt the point, B situation is a bit more complicated. In this case force of gravity and centrifugal force are not aligned. We have to look at y components of this forces, y-axis, in this case, is just pointing upward.
Part CThe child will stay in place at point A when centrifugal force and force of gravity are in balance:
Answer:
The force they will exert on each other is 1.6*10⁻¹⁰ N
Explanation:
The electromagnetic force is the interaction that occurs between bodies that have an electric charge. When the charges are at rest, the interaction between them is called the electrostatic force. Depending on the sign of the interacting charges, the electrostatic force can be attractive or repulsive. The electrostatic interaction between charges of the same sign is repulsive, while the interaction between charges of the opposite sign is attractive.
Coulomb's law is used to calculate the electric force acting between two charges at rest. This force depends on the distance "r" between the electrons and the charge of both.
Coulomb's law is represented by:

where:
- F = electric force of attraction or repulsion in Newtons (N). Like charges repel and opposite charges attract.
- k = is the Coulomb constant or electrical constant of proportionality.
- q = value of the electric charges measured in Coulomb (C).
- r = distance that separates the charges and that is measured in meters (m).
In this case:
- k= 9*10⁹

- q1= 1.602*10⁻¹⁹ C
- q2= 1.602*10⁻¹⁹ C
- r= 1.2*10⁻⁹ m
Replacing:

and solving you get:
F=1.6*10⁻¹⁰ N
<u><em>The force they will exert on each other is 1.6*10⁻¹⁰ N</em></u>
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Answer with Explanation:
We are given that
Mass of one cart,
Mass of second cart,
Initial velocity of one cart,
Initial velocity of second cart,
a.Total momentum,

b.Velocity of second cart,
=0
According to law of conservation of momentum
Initial momentum=Final momentum


