Answer: The force constant k is 10600 kg/s^2
Step by step:
Use the law of energy conservation. When the elevator hits the spring, it has a certain kinetic and a potential energy. When the elevator reaches the point of still stand the kinetic and potential energies have been transformed to work performed by the elevator in the form of friction (brake clamp) and loading the spring.
Let us define the vertical height axis as having two points: h=2m at the point of elevator hitting the spring, and h=0m at the point of stopping.
The total energy at the point h=2m is:

The total energy at the point h=0m is:

The two Energy values are to be equal (by law of energy conservation), which allows us to determine the only unknown, namely the force constant k:

Gravity is pulling the book towards the center of the earth, and the rebounding effect of the table cancelling out gravity allowing for the book to sit at rest.
Answer:
The field will remain the same
Explanation:
This is because electric field given as
E1= kq1/r²
And that of second charge
E² = kq2/r²
Is not affected by the size of the second charge q2
Answer:
they will drop at the same time
Explanation:
projectile motion consists of two components, horizontal and vertical, which are independent of one another. That means that if you drop a ball and kick another one straight out, they will both hit the ground at the same time so long as they have the same initial drop height .