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(C) The person’s rotational inertia is un-
changed.
(D) The person’s angular velocity is un-
changed.
(E) The person’s angular momentum in-
creases.
74. A pith ball electroscope possesses a certain
charge. A charged glass rod is then held close
to the electroscope. The pith ball moves no-
ticeably toward the glass rod. Which of the
following accounts for such an interaction?
(A) There are subtle gravitational forces be-
tween the glass rod and the pith ball.
(B) The glass rod and the pith ball each pos-
sess a net positive charge.
(C) The glass rod and the pith ball each pos-
sess a net negative charge.
(D) The glass rod and the pith ball are op-
positely charged.
(E) The glass rod mass greatly exceeds the
mass of the pith ball.
75. A total of 100 J of energy is supplied to a ma-
chine. The machine is then capable of displac-
ing a 30N object 1.5m. What is the approxi-
mate efficiency of the machine?
(A) 15%
(B) 20%
(C) 30%
(D) 45%
(E) 60%
STOP
IF YOU FINISH BEFORE TIME IS CALLED,
YOU MAY CHECK YOUR WORK ON THIS
TEST ONLY. DO NOT WORK ON ANY
OTHER TEST IN THIS BOOK.

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Physics Subject Test
319
ARCO
■ SAT II Subject Tests
w w w . p e t e r s o n s . c o m / a r c o
ANSWER KEY
EXPLANATORY ANSWERS
1. The correct answer is (E). Definition.
2. The correct answer is (B). Definition.
3. The correct answer is (D). Definition.
4. The correct answer is (B). See diagram below:
5. The correct answer is (C). The ammeter measures current. Recall that the unit of current is
the ampere.