Mr. Dewey and Mr. Kehr decided to demonstrate a half atwoods machine to their students. During the winter when the roof of the school froze over, they attached a pulley to the edge of the roof. Mr. Dewey sat in a chair on the roof and attached a rope to the chair and had Mr. Kehr grab the other end and step off the roof. Mr. Kehr has a mass of 50 Kg, and Mr. Dewey has a mass of 70 Kg.