A physics textbook is launched up a rough incline with a kinetic energy of 200 joules. When the book comes momentarily to rest near the top of the incline, it has only gained 180 joules of gravitational potential energy. About how much kinetic energy will it have when it returns to the launch point?

Answer 1

KE -PE = 200 -180 = W(fr).
PE = W (fr) = 180 -20 = 160J

Answer 2

xixixixixixi i donnot know