International Young Physicists' Tournament (IYPT), is one of the most prestigious international physics contests among high school students. This book is based on the solutions of 2015 IYPT problems. The authors are undergraduate students who participated the CUPT (Chinese Undergraduate Physics Tournament). It is intended as a college level solution to the challenging open-ended problems. It provides original, quantitative solutions in fulfilling seemingly impossible tasks. The young authors provide quantitative solutions to practical problems in everyday life.This is a good reference book for undergraduates, advanced high school students, physics educators and curious public interested in the intriguing phenomenon in daily life.