Image formed by a plane mirror is always virtual which means that the light rays do not actually come from the image but upright and these of the same shape and size are the object it is<span> reflecting.</span>
A force of 43.8 N is required to stretch the spring a distance of 15.5 cm = 0.155 m, so the spring constant <em>k</em> is
43.8 N = <em>k</em> (0.155 m) ==> <em>k</em> = (43.8 N) / (0.155 m) ≈ 283 N/m
The total work done on the spring to stretch it to 15.5 cm from equilibrium is
1/2 (283 N/m) (0.155 m)² ≈ 3.39 J
The total work needed to stretch the spring to 15.5 cm + 10.4 cm = 25.9 cm = 0.259 m from equilibrium would be
1/2 (283 N/m) (0.259 m)² ≈ 9.48 J
Then the additional work needed to stretch the spring 10.4 cm further is the difference, about 6.08 J.
When you talk about Hooke's law, it always have to do something with springs. Hooke's Law, from Robert Hooke, saw a relation between the force applied to the spring and the extension of its length. The equation is: F = kx, where k is the spring constant and x is the displacement of the original and stretched lengths. In other words, x is the length of deformation. Hence, the object must be elastic to come up with a displacement or deformation, in the first place. Then, the Hooke's Law is only applicable to elastic materials.
