Which of the following is not an example of potential energy?
a. The energy stored in a pile driver.
b. The energy stored in a stretched spring.
c. The energy of a body moving across a horizontal surface.
d. The energy in the water at the top of a waterfall.
c
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Mass on a Spring: When a laboratory sample of unknown mass is placed on a vertical spring-scale having a force constant (spring constant) of 467 N/m, the system obeys the equation y = (4.4 cm) cos(33.3 s-1 t). What is the mass of this laboratory sample?
Fill in the blank(s) with the appropriate word(s).
The distance between Earth and the Moon is 3.84 108 m. A pulse of laser light aimed at the Moon that bounces back to Earth undergoes a round-trip time of about
A) zero seconds. B) less than 1 second. C) two and a half seconds. D) three seconds.
A heavy box is located in the center of the cargo hold of a train. There are no other boxes or items in the cargo hold and there are no straps holding the box down. The train accelerates along the track in the northward direction. The direction of the friction force exerted by the floor of the cargo hold on the box is
1.upward. 2.none; no friction force exists because the box is not sliding. 3.to the north. 4.to the south.
A billiard ball is moving in the x direction at 30.0 cm/s and strikes another billiard ball moving in the y direction at 40.0 cm/s. As a result of the collision, the second ball moves at 50.0 cm/s, and the first ball stops. In what final direction does the second ball move?
a. in the x direction b. at an angle of 45.0o ccw from the x direction c. at an angle of 53.1o ccw from the x direction d. Such a collision cannot happen.