A piece of rope is pulled by two people in a tug-of-war. Each exerts a 400-N force. What is the tension in the rope?
A) zero
B) 400 N
C) 600 N
D) 800 N
E) none of the above
Answer: B
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Surface air blowing inward to a center of low pressure can rise, expand, and
A) cool, often condensing into clouds that produce precipitation. B) warm, producing generally clear skies. C) cool, producing generally clear skies. D) warm, often condensing into clouds that produce precipitation.
Two long parallel wires carry currents of 10 A in opposite directions
They are separated by 40 cm. What is the magnitude of the magnetic field in the plane of the wires at a point that is 20 cm from one wire and 60 cm from the other? (?0 = 4? × 10-7 T ? m/A) A) 1.5 µT B) 3.3 µT C) 6.7 µT D) 33 µT E) 67 µT
Which of the following statements about rich clusters of galaxies (those with thousands of galaxies) is not true?
A) They are sources of X-ray emission due to the presence of hot, intergalactic gas. B) There likely have been numerous collisions among the member galaxies at some time in the past. C) Galaxies in the central regions are predominantly spirals, while elliptical galaxies roam the outskirts. D) They often have a very large, central dominant galaxy near their center, perhaps formed by the merger of several individual galaxies. E) The speeds of the galaxies in the cluster indicate that most of the cluster mass is dark matter.
The observation that materials expand in size with an increase in temperature can be applied to what proportion of existing substances?
a. 100% c. few b. most d. none