Answer:
The spike will remain at 3ft above the ground after 30 years because the tree's growth in height does not cause the spike to increase in height.
Please find the detailed explanation below
Step-by-step explanation:
According to this question, a 20 foot tree was taken and a spike was hammered into 3 feet above the ground. After 30 years, the tree grew 100ft tall. Note that the spike will remain 3ft above the ground after 30 years.
This is because, unlike a tree which is a living thing and possess the characteristics to undergo growth (in width and height), the spike is a non-living thing and hence, cannot grow. Therefore, the spike will remain where it was (3feet above the ground) in years to come.
Also, note that, the spike will not move in height as the tree grows. This is because a tree grows from the tips or apical region i.e. the cell division that brings about growth of a plant occurs at the tips, hence, the tree will continue to elongate upwards leaving the Spike where it is.