A block of mass M slides down a frictionless plane inclined at an angle ? with the horizontal. The gravitational force is directed
A) parallel to the plane in the same direction as the movement of the block.
B) parallel to the plane in the opposite direction as the movement of the block
C) perpendicular to the plane.
D) toward the center of the Earth.
E) toward the center of mass of the block.
D
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An un-stretched hanging spring is 50 cm long. Suspending a 100-N block from it increases its length to 60 cm. Adding another 100-N block makes the spring's length
A) 60 cm. B) 70 cm. C) 80 cm. D) 100 cm. E) 120 cm.
The speed of a vertically-thrown ball at the top of its path is
A) zero. B) 10 m/s2. C) between zero and 10 m/s2. D) dependent on the mass of the ball.
A real experiment, analogous to the "twin paradox," has actually been done in order to check the predictions of Einstein's relativity. In the experiment,
A) a mass took a trip in a jet plane, while a second identical mass stayed on the ground. B) two kilograms oscillated on springs, one of them in on Earth and the other in a space satellite. C) a mouse went on a jet airplane trip and returned, while a second mouse stayed on the ground. D) a human took a trip in a space satellite, while a second human stayed on Earth. E) an atomic clock took a trip on a jet plane, while an identical clock stayed on the ground.
Plane polarized light is sent through two consecutive polarizers, the first having its plane of polarization in the same direction as the incident light and the second having its plane at 90° to the original plane of polarization. A third polarizer, with plane of polarization at 60° to the original plane of polarization, is placed between the two other polarizers. What fraction of the original
intensity now gets through? a. 0.56 c. 0 b. 0.19 d. 0.25