After the PHYS-2200-01 Mid-Term Exam, Hector decides to push his 10 kg hard copy
ID: 1780831 • Letter: A
Question
After the PHYS-2200-01 Mid-Term Exam, Hector decides to push his 10 kg hard copy of the class textbook a distance h = 1.0 meters across the top of his desk, which has a kinetic coefficient of friction Mu_k = 1.0. On pushing it h = 1.0 m, it just reaches the desktop edge, and it falls abruptly, and gloriously, into the bottom of the trashcan right next to his desk. The bottom of the trashcan is a distance H below the top of his desk. If Hector's work in pushing the textbook across the desk equals the gravitational potential energy of the textbook just after leaving the edge of the desk, determine the exact value for the height of the desk, H, above the bottom of the trash can. Select one: a. H = 3h b. H = 2h c. H = h d. Impossible to tell; Hector isn't strong enough to push the heavy book that far!
Explanation / Answer
Work done in pushing the textbook through a distance h, W = Mu_k * 10*g*h
Potential energy of the text book when it is at the top of the table, PE = 10*g*H
Now as per the given condition equalize the two -
W = PE
=> Mu_k * 10*g*h = 10*g*H
=> H = Mu_k*h
put Mu_k = 1 (as given)
So, H = h
So, option (c) is the correct answer.