If a frictional force acts on the child, what is the magnitude of the mechanical energy dissipated by this force, if the speed of the child at the bottom is 9.7 m/s

Asun-sized star will spend most of its lifetime as a: white dwarf red giant protostar main-sequence star

Light from the sun reaches the earth in 8.3 minutes. the velocity is 3.00 x 10^8 m/s. how far is earth from the sun? i know how to get to d = (3 x 10^8 m/s)(498 sec). i just don't know how to get from there to the answer being 1.5 x 10^11 m.

Acoil suspended freely, points in some direction when no current is passed through it . can you tell what will happen when a current is passed though it?