You are working in a library, reshelving books. You lift a book from the floor to the top shelf. The kinetic energy of the book on the floor was zero, and the kinetic energy of the book on the top shelf is zero, so there is no change in kinetic energy. Yet you did some work in lifting the book. Is the work-kinetic energy theorem violated?
1.Yes, it is violated because a force acting on the book should change the book's kinetic energy.
2.No, it is not violated because the book really does have a final velocity, but so does the entire system, so it is impossible to detect the book's motion.
3.Yes, it is violated because a force that acts on the book should change the book's velocity.
4.No, it is not violated because there are two forces that act on the book. One is the downward force that the Earth exerts on the book, which is counterbalanced by the upward force that you exert on the book. The total work done on the book, therefore, is zero, and is equal to its overall change in kinetic energy.
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An object is released from rest when it is a height h above the surface of a planet of mass M and radius R. What is the speed of the object just before striking the surface of the planet? Neglect any air resistance. Let h = 4.0 × 10^6 m, R = 5.0 × 10^6 m, and M = 4.0 × 10^24 kg
a. 7.8 km/s b. 3.5 km/s c. 5.4 km/s d. 6.9 km/s e. 4.8 km/s
Match the moons listed to the left with the characteristics described in the sentences to the right. Drag words from the left to the blanks on the right. Each moon should be used only once.
Calorimetry: A 0.600-kg piece of metal X is heated to 100°C and placed in an aluminum can of mass 0.200-kg which contains 0.500 kg of water initially at 17.3°C. The final equilibrium temperature of the mixture is 20.2°C, what is the specific heat of metal X? The specific heats of water and aluminum are 4186 J/kg ? K (water) and 910 J/kg ? K (aluminum).
A. 140 J/kg ? K B. 270 J/kg ? K C. 450 J/kg ? K D. 900 J/kg ? K
In a photo like the Hubble Deep Field (Figure 16.1 in your textbook), we see galaxies in many different stages of their lives. In general, which galaxies are seen in the earliest (youngest) stages of their lives?
A) the galaxies that have the most hot, young O and B stars B) the galaxies that are the reddest in color C) the galaxies that are farthest away D) the galaxies that are nearest to us