Answer:
The spring constant of this spring is 200 N/m.
Explanation:
Given:
Original unstretched length of the spring (x₀) = 10 cm =0.10 m [1 cm =0.01 m]
Stretched length of the spring (x₁) = 18 cm = 0.18 cm
Force acting on the spring (F) = 16 N
Spring constant of the spring (k) = ?
First let us find the change in length of the spring or the elongation caused in the spring due to the applied force.
So, Change in length = Final length - Initial length

Now, restoring force acting on the spring is directly related to its elongation or compression as:

Rewriting in terms of 'k', we get:

Now, plug in the given values and solve for 'k'. This gives,

Therefore, the spring constant of this spring is 200 N/m.
Answer:

Explanation:
According to Coulomb's law, the magnitude of the electric force between two equals charges (q) is given by:

Here k is the coulomb constant and d is the distance between the charges. For two electrons we have:

Its a solar cell. Photo voltaic Cell is also known as a solar cell.
I don't think an object can exert a force on itself.
Try it: Get up on a skateboard, and see if you can do anything to yourself that makes you start moving ... without touching anything else.
It'll be easy to tell if you succeed. If you actually do exert an unbalanced force on yourself, then you'll begin to accelerate.