why does cobalt chloride strip turn pink or blue?

Answer 1

It indicates the amount of water present in the sample, by going back and forth between a hydrated and anhydrous form. Each has a different color.

http://en.wikipedia.org/wiki/Cobalt(II)_chloride

Answer 2

1. Two dogs are fighting over a 0.5 kg bone. The larger dog pulls on the bone in one direction with a force of 40 N. The smaller dog pulls in the opposite direction with a force of 36 N. What is the net force on the bone?