Aspring contains 1.6 j of elastic potential energy when it is extended by 0.40m. what is it's spring constant?

The elastic potential energy of a spring is given by the expression , where k is the spring constant and x is the extension of spring.

So we have

   PE = 1.6 Joule

  x = 0.40 meter

 Substituting

So spring constant K = 20 N/m

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.

answer and explanation;