Is there an intuitive explanation why a circle is not contractible?
131519
intuition on the fundamental group of $S^1$
115139
Use my example to explain why loop diagram will not occur in classical equation of motion?
93263
Can contractible subspace be ignored/collapsed when computing $\pi_n$ or $H_n$?
20872
Is it possible for a physical object to have an irrational length?
14391
Elastic collision between two circles
95728
The union of growing circles is not homeomorphic to wedge sum of circles
5055
Why does this object periodically turn itself?
151950
Why is indiscrete topology unmetrizable?
133978
Mechanics of Horizontal Stretching and Shrinking
5086
Why is the derivative of a circle's area its perimeter (and similarly for spheres)?
99740
Why is it "geometric" but "theoretical"?
97768
Why is $R\cos{a} = mg$ in circular motion compared and not $R = mg\cos{a}$?
75980
What if the net force provided for a circular motion is larger than the required centripetal force?
149770
Connect a circle and a line together
1921
How is circular motion possible on a banked road when there is no Friction?
137051
Ball swung in a horizontal circle, can the string ever by exactly horizontal to the ground?
15421
Is any work done if I walk in a circle?