Problem 1: For all of the following problems,imagine a crane that is lifting a weight of mass m through a heighth at constant speed, and consider the following three choices ofsystem:
(1) system is the weight only; (2) system is the weightand the earth; (3) system is the crane only.
For each of these choices, and in this order, what is the network done on the system by the external forces (Wext,sys) in theprocess considered?
(a) (1) 0; (2) mgh; (3) −mgh
(b) (1) mgh; (2) 0; (3) −mgh
(c) (1) −mgh; (2) mgh; (3) 0
(d) (1) 0; (2) mgh; (3) 0
Problem 2: For system (1) (weight only), whichof the following is a correct statement of the energy changes goingon inside the system during the process described?
(a) ∆Esource + ∆Ediss = −mgh
(b) ∆U G = mgh
(c) ∆K = 0
(d) ∆Ediss = mgh
Problem 3: For system (2) (weight and earth),which of the following is a correct statement of the energy changesgoing on inside the system during the process described?
(a) ∆Esource + ∆Ediss = −mgh
(b) ∆U G = mgh
(c) ∆K = 0
(d) ∆Ediss = mgh
Problem 4: For system (3) (crane only), whichof the following is a correct statement of the energy changes goingon inside the system during the process described?
(a) ∆Esource + ∆Ediss = −mgh
(b) ∆U G = mgh
(c) ∆K = 0
(d) ∆Ediss = mgh
Problem 5: If it takes a time ∆t to raise theweight through the height h, what is the power output of the cranefor that process?
(a) mg (b) mgh (c) mgh/∆t (d) 0
