The emergence of terrestrial life—for example, land plants, came about during the
A) Triassic.
B) Silurian.
C) Ordovician.
D) Carboniferous era.
Answer: B
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Two equal-magnitude forces are exerted to a door at the doorknob. The first force is exerted perpendicular to the door, and the second force is exerted at 30° to the plane of the door. Which force exerts the greater torque about the door hinge?
A) the first force (exerted perpendicular to the door) B) the second force (exerted at an angle) C) Both forces exert equal non-zero torques. D) Both forces exert zero torque.
Does an electric field exert a force on a beam of moving electrons? Assume the motion of the electrons is along the x axis and field is in the y direction
1.yes 2.no
A square conducting loop is situated such that it is vertical, in the x-z plane. The earth’s gravitational field points downward (in the –z direction). The loop is dropped, and maintains its orientation in the x-z plane. A magnetic field pointing in the +y direction exists and is uniform with respect to time, but varies as a function of z: B(z)=Bo (10m-z). The loop is dropped and allowed to fall under the influence of gravitation. You observe the loop from the +y direction. Which of the following occurs?
A. The situation is unclear because we do not know the initial conditions. B. There is a clockwise induced current. C. There is a counter-clockwise induced current. D. There is no induced current.
The planets are seen in the Zodiac constellations because:
a) they reach the zenith at noon during the fall equinox b) they orbit the Earth just like the Sun does c) they orbit the Sun in the same plane as the Earth does d) they reach the meridian at noon during the summer solstice e) they reach the zenith at noon during the summer solstice