A 2.0-m2 Thermopane window is constructed, using two layers of glass 4.0 mm thick, separated by an air space of 5.0 mm. If the temperature difference is 20°C from the inside of the house to the outside air, what is the rate of heat flow through this window? (Thermal conductivity for glass is 0.84 W / m •°C and for air 0.0234 W / m •°C.)
a. 7700 W
c. 180 W
b. 90 W
d. 550 W
C
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A butterfly moves with a speed of v = 12.0 m/s. The x-component of its velocity is 8.00 m/s. The angle between the direction of its motion and the x-axis must be
A) 60.0° B) 41.8° C) 48.2° D) 30.0° E) 53.0°
The first of two identical boxes of mass m is sitting on level ground. The second box is sitting on a ramp that makes an angle with the ground. When a force of magnitude F is applied to each box in a direction parallel to the surface it is on, upwards on the box on the ramp, neither box moves. Which statement comparing the friction force on the box on the level, Fs,L, to the friction force on the
box on the ramp, Fs,R, is correct?
a. Fs,R = Fs,L.
b. Fs,R > Fs,L.
c. Fs,R
A car travels along the perimeter of a vertical circle (radius = 0.25 km) at a constant speed of 30 m/s. What is the magnitude of the resultant force on the 60-kg driver of the car at the lowest point on this circular path?
a. 0.37 kN b. 0.80 kN c. 0.22 kN d. 0.59 kN e. 0.45 kN
A capacitor of capacitance C takes 2 s to reach 63% of its maximum charge when connected in series to a resistance R and a battery of emf
How long does it take (from zero initial charge) for this capacitor to reach 95% of its maximum charge? A) 3 s B) 5 s C) 7 s D) 4 s E) 6 s