A uniform rod is hinged to a wall and held at a 30° angle by a thin string that is attached to the ceiling and makes a 90° angle to rod. Which statement(s) must be true? (At least one of them is true and at least one is false.)
1.The hinge force is purely vertical.
2.The hinge force is purely horizontal.
3.The string tension is equal to the hinge force.
4.The string tension is smaller than the rod's weight.
5.1 and 3 are true.
6.2 and 3 are true.
7.1 and 4 are true.
8.2 and 4 are true.
9.3 and 4 are true.
10.Three of the statements are true.
4
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How can we tell that some stars are relatively close to us in the sky?
a. Some stars are occasionally eclipsed by the Moon, so they must be nearby. b. Some stars vary in brightness caused by sunspots we can see because they are so close. c. Some stars appear to be extremely bright and must therefore be very close to us. d. Some stars appear to move periodically back and forth against the background stars because of Earth's movement around the Sun.
The figure shows the graph of 
versus time for an object moving along the x-axis. Solve graphically for the distance traveled between t = 5.0 s and t = 9.0 s.
A. 110 m
B. 120 m
C. 100 m
D. 130 m
The length of the Appalachian Trail is 2,015 miles. How long is it in kilometers?
A) 3,245 km B) 1,251 km C) 3,112 km D) 1,008 km E) 963 km
A theory in the field of science is
A) an educated guess. B) less than a fact. C) a synthesis of a large body of well-tested knowledge. D) unchangeable.