A bullet is fired with a certain velocity at an angle ? above the horizontal at a location where g = 10.0 m/s2. The initial x- and y-components of its velocity are 86.6 m/s and 50.0 m/s respectively
At what angle is the bullet fired above the horizontal? A) 45.0°
B) 60.0°
C) 30.0°
D) 90.0°
E) 75.0°
C
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A Trombe wall is a masonry wall often used in passive solar homes to store solar energy. Suppose that such a wall, fabricated from 20-cm-thick solid concrete blocks (k = 0.13 W/(mK), ? = 0.05 × 10–5 m2/s) is initially at 15°C in equilibrium with the room in which it is located. It is suddenly exposed to sunlight and absorbs 500 W/m2 on the exposed face. The exposed face loses heat by radiation and convection to the outside ambient temperature of –15°C through a combined heat transfer coefficient of 10 W/(m2 K). The other face of the wall is exposed to the room air through a heat transfer coefficient of 10 W/(m2 K). Assuming that the room air temperature does not change, determine the maximum temperature in the wall after 4 hours of exposure and the net heat transferred to the room.
GIVEN • Trombe wall suddenly exposed to sunlight FIND (a) Maximum temperature in the wall after 4 hours (b) Heat input to the room
A refrigerator uses 40 J of work to extract heat from a heat reservoir at 
If the coefficient of performance of the refrigerator is 2.1, then how much heat is extracted from the heat reservoir at 
A. 48 J B. 65 J C. 84 J D. 90 J
Our senses may obtain less-than-accurate information concerning our physical world because they
a. have limited sensitivity. b. have a limited range. c. are useless. d. can be deceived.
A characteristic of shield volcanoes is the formation of a crater at the summit which occurs when:
A) the volcano erupts explosively. B) the lava withdraws and the surface collapses. C) the lava flows melt through the thin crust of the peak. D) the underlying hot spot suddenly turns on. E) the volcano is impacted by a large meteorite.