The force of repulsion between the two object is <u><em>9*10¹⁵ N</em></u>
Explanation:
Coulomb's law indicates that charged bodies suffer a force of attraction or repulsion when approaching. The value of said force is proportional to the product of the value of its loads and inversely proportional to the square of the distance that separates them. This is expressed mathematically by the expression:
where:
F is the electrical force of attraction or repulsion. In the International System it is measured in Newtons (N).
Q and q are the values of the two point charges. In the International System they are measured in Culombios (C).
r is the value of the distance that separates them. In the International System it is measured in meters (m).
K is a constant of proportionality called constant of Coulomb's law. It depends on the medium in which the loads are located. For vacuum K is approximately 9*10⁹ in the International System.
From this law it is possible to predict the electrostatic force of attraction or repulsion between two particles according to their electrical charge and the distance between them.
The force will be of attraction if the charges are of opposite sign and of repulsion if they are of the same sign.
In this case:
Q=q= 1 C
r=1 mm= 0.001 m
Then:
So:
F=9*10¹⁵ N
<u><em>The force of repulsion between the two object is 9*10¹⁵ N</em></u>
When standing on the bathroom scale within the moving elevator, there are two forces acting on Henry's mass: Normal force and gravity.
Gravity is always downward, and normal force is perpendicular to the surface on which the mass is located (the bathroom scale), in upward direction.
Normal force, can adopt any value needed to match the acceleration of the mass, according to Newton's 2nd Law.
Gravity (which we call weight near the Earth's surface) can be calculated as follows:
According to Newton's 2nd Law, it must be met the following condition:
As the gravity is larger than normal force, this means that the acceleration is downward, so, we choose this direction as the positive.
Solving for a, we get:
We can find the speed after the first 3.8 s (assuming a is constant), applying the definition of acceleration as the rate of change of velocity:
Now, if during the next 3.8 s, normal force is 930 N (same as the weight), this means that both forces are equal each other, so net force is 0.
According to Newton's 2nd Law, if net force is 0, the object is either or at rest, or moving at a constant speed.
As the elevator was moving, the only choice is that it is moving at a constant speed, the same that it had when the scale was read for the first time, i.e., 4 m/s downward.
