Review of the woman, the barbell, and the Earth (Section 7.9 in the textbook). Starting from rest, a woman lifts a barbell with a constant force F through a distance h, at which point she is still lifting, and the barbell has acquired a speed v. Let Ewoman stand for the following energy terms associated with the woman: Ewoman = Echemical, woman + Kwoman (moving arms etc.) + Ugrav, woman+Earth + Ethermal, woman
The change in the kinetic energy of the barbell is (1/2)mv2 - 0 = (1/2)mv2.
The general statement of the energy principle is deltacapEsys = Wext. We'll consider terms on the left side of the equation (the deltacapEsys side, changes in the energy inside the system) and terms on the right side (the Wext side, energy inputs from the surroundings).
I. System: Woman + barbell + Earth For the system consisting of the woman, the barbell, and the Earth, which of the following terms belong on the left side of the energy equation (the deltaEsys side)?
deltaEwoman
-mgh
-Fh
Fh
-(1/2)mv2
+mgh
none of these terms (left side is 0)
(1/2)mv2
For the system consisting of the woman, the barbell, and the Earth, which of the following terms belong on the right side of the energy equation (the Wext side)?
Fh
-mgh
+mgh
-(1/2)mv2
deltaEwoman
-Fh none of these terms (right side is 0)
(1/2)mv2
II. System: barbell only For the system consisting of the barbell only, which of the following terms belong on the left side of the energy equation (the deltacapEsys side)?
eltacapEwoman
-mgh
+mgh
-(1/2)mv2
Fh (
1/2)mv2 n
one of these terms (left side is 0)
-Fh
For the system consisting of the barbell only, which of the following terms belong on the right side of the energy equation (the Wext side)?
-Fh
-mgh
+mgh
(1/2)mv2
-(1/2)mv2
Fh
none of these terms (right side is 0)
deltaEwoman
III. System: barbell + Earth For the system consisting of the barbell and the Earth, which of the following terms belong on the left side of the energy equation (the Esys side)?
-Fh
-(1/2)mv2
Fh
(1/2)mv2
none of these terms (left side is 0)
deltacapEwoman
+mgh
-mgh
For the system consisting of the barbell and the Earth, which of the following terms belong on the right side of the energy equation (the Wext side)?
1/2)mv2
deltacapEwoman
+mgh
-(1/2)mv2
none of these terms (right side is 0)
Fh
-mgh
-Fh