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(A) An attractive force exists.
(B) A repulsive force exists.
(C) No force exists.
(D) Forces generated by each wire are always
in the same direction.
(E) Forces violate Newton’s third law of mo-
tion.
63. An astronaut orbits the earth in a space shuttle.
In this orbit, the astronaut feels “weightless.”
Which of the following best explains such
weightlessness?
(A) Absence of gravity
(B) Loss of frictional forces
(C) Astronaut and space shuttle both accel-
erate toward earth
(D) Gravitational forces affect space shuttle only
(E) No external forces act on space shuttle
64. The linear momentum of an object at time t is
zero. Which of the following quantities is also
necessarily equal to zero?
I.
Velocity
II.
Kinetic energy
III. Potential energy
(A)
I only
(B)
II only
(C)
I and II only
(D)
I and III only
(E)
I, II, and III
65. A 10 kg object is acted on by only two.forces,
as illustrated above. If the object’s acceleration
is 1 m/s
2
to the left, what is the net force on the
object?
(A) 0.1N to the right
(B) 0.1N to the left
(C) 10N to the right
(D) 10N to the left
(E) 100N to the left
59. The indices of refraction for pairs of media
are given below. In each case, light rays origi-
nate in medium 1 and are incident upon the
surface of medium 2. Total internal reflection
cannot occur in which pair?
Index of Refraction
Medium 1
Medium 2
(A)
1.33
1.00
(B)
1.38
1.33
(C)
1.49
1.77
(D)
1.65
1.36