Question

A student imagines a wite stretched aroun the earth. She says that if the wire is cut, its length is increased by 20 m, and it is restreched around earth, then the talles person alive could walk under it. Do you agree with her? Why or Why not?

Answer 1

Yes, we agree to that student.  
The shape of the earth is spherical (to some extent). Center part (diameter) is the widest and it narrows down if we move away from the center ( either upwards or downwards).

In first case, we can assume that the wire is stretched around the earth at its diameter (the widest part).

In second case, the wire is cut and restretched. Let us assume, that wire is restretched towards upper side of the earth as the tallest man can walk under it. The upper side is smaller than the diameter therefore the same length of wire can be stretched around the earth and 20m wire is still left.