A 1.6-kg block slides down a plane (inclined at 25° with the horizontal) at a constant speed of 2.0 m/s. At what rate is the frictional force changing the mechanical energy of the block?
a. +28 W
b. +13 W
c. ?13 W
d. ?28 W
e. +6.5 W
c
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Which of the following is an example in which you are traveling at constant speed but not at constant velocity?
A) rolling freely down a hill in a cart, traveling in a straight line B) driving backward at exactly 50 km/hr C) driving around in a circle at exactly 100 km/hr D) jumping up and down, with a period of exactly 60 hops per minute E) none of the above
Has Polaris always been the "North Star"?
A) No, because the Earth's axis slowly changes the direction it points. B) Yes, because the stars are unchanging. C) No, because it is a young star that only formed a few hundred years ago. D) No, because the Milky Way blocked our line of site to it for a long time.
In order to jump off the floor, the floor must exert a force on you
a. in the direction of and equal to your weight. b. opposite to and equal to your weight. c. in the direction of and less than your weight. d. opposite to and less than your weight. e. opposite to and greater than your weight.
In a Galilean telescope, the eyepiece is a diverging lens, while the objective lens is a converging lens. This means that:
A. The image that the observer looks at is inverted B. The image that the observer looks at subtends a larger angle than the object does C. The image that the observer looks at is virtual D. The image that the observer looks at is real