Hot Air in a Physics Lecture. (a) A typical student listening attentively to a physics lecture has a heat output of 100 W. How much heat energy does a class of 140 physics students release into a lecture hall over the course of a 50-min lecture? (b) Assume that all the heat energy in part (a) is transferred to the 3200 m 3 of air in the room. The air has specific heat 1020J/kg·K and density 1.20 kg/m 3 . If none of the heat escapes and the air conditioning system is off, how much will the temperature of the air in the room rise during the 50-min lecture? (c) If the class is taking an exam, the heat output per student rises to 280 W. What is the temperature rise during 50 min in this case?
Hot Air in a Physics Lecture. (a) A typical student listening attentively to a physics lecture has a heat output of 100 W. How much heat energy does a class of 140 physics students release into a lecture hall over the course of a 50-min lecture? (b) Assume that all the heat energy in part (a) is transferred to the 3200 m 3 of air in the room. The air has specific heat 1020J/kg·K and density 1.20 kg/m 3 . If none of the heat escapes and the air conditioning system is off, how much will the temperature of the air in the room rise during the 50-min lecture? (c) If the class is taking an exam, the heat output per student rises to 280 W. What is the temperature rise during 50 min in this case?
Hot Air in a Physics Lecture. (a) A typical student listening attentively to a physics lecture has a heat output of 100 W. How much heat energy does a class of 140 physics students release into a lecture hall over the course of a 50-min lecture? (b) Assume that all the heat energy in part (a) is transferred to the 3200 m3 of air in the room. The air has specific heat 1020J/kg·K and density 1.20 kg/m3. If none of the heat escapes and the air conditioning system is off, how much will the temperature of the air in the room rise during the 50-min lecture? (c) If the class is taking an exam, the heat output per student rises to 280 W. What is the temperature rise during 50 min in this case?
Children playing in a playground on the flat roof of a city school lose their ball to the parking lot below. One of the teachers kicks the ball back up to the children as shown in the figure below. The
playground is 6.10 m above the parking lot, and the school building's vertical wall is h = 7.40 m high, forming a 1.30 m high railing around the playground. The ball is launched at an angle of
8 = 53.0° above the horizontal at a point d = 24.0 m from the base of the building wall. The ball takes 2.20 s to reach a point vertically above the wall. (Due to the nature of this problem, do not
use rounded intermediate values-including answers submitted in WebAssign-in your calculations.)
(a) Find the speed (in m/s) at which the ball was launched.
18.1
m/s
(b) Find the vertical distance (in m) by which the ball clears the wall.
0.73
✓ m
(c) Find the horizontal distance (in m) from the wall to the point on the roof where the ball lands.
2.68
m
(d) What If? If the teacher always launches the ball…
It is not possible to see very small objects, such as viruses, using an ordinary light microscope. An electron microscope can view such objects using an electron beam instead of a light beam. Electron microscopy has proved invaluable for investigations of viruses, cell membranes and subcellular structures, bacterial surfaces, visual receptors, chloroplasts, and the contractile properties of muscles. The "lenses" of an
electron microscope consist of electric and magnetic fields that control the electron beam.
As an example of the manipulation of an electron beam, consider an electron traveling away from the origin along the x axis in the xy plane with initial velocity ₁ = vi. As it passes through the region x = 0 to x=d, the electron experiences acceleration a = ai +a, where a and a, are constants. For the case v, = 1.67 x 107 m/s, ax = 8.51 x 1014 m/s², and a = 1.50 x 10¹5 m/s², determine the following at
x = d = 0.0100 m.
(a) the position of the electron
y, = 2.60e1014
m
(b) the…
Chapter 17 Solutions
University Physics, Volume 2 - Technology Update Custom Edition for Texas A&M - College Station, 2/e
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