1. In calculating the work W necessary to stretch a spring from its natural length of 8 centimeters to a length of 12 centimeters, we need some more information about the spring. There are two distinct kinds of information, each of which separately would provide the necessary assistance so we could find W. Describe what the two additional kinds of information are.

* displacement from equilibrium position

* The spring constant,

Explanation:

The work done by a spring is two times the expressions

         W = ∫ F. dx

in a spring the force is given by hooke's law

          F = - k Δx

we substitute

         W = - k ∫ x dx cos θ

In the case of the spring, the displacement is in the same direction of work, therefore the angle is zero and the cosine is equal to 1

we integrate

           W = ½ k Δx²

we can see that we need two parts to calculate the work

* displacement from equilibrium position

          Δx = 12 -8 = 4 cm

* The spring constant, this constant can be found from the displacement measurements as a function of the applied force.

fgravity=10x10=100n case 1

fgravity=30x20=600n case 2

6 times more