A small sphere is allowed to fall through air, and when the sphere has a speed of 4.8 × 10^–4 m/s, the viscous force on the sphere is 3.0 × 10^–15 N. If the viscosity of air is 1.4 × 10^–5 N·s/m2, what is the radius of the drop?
a. 2.4E–8 m
b. 8.4E–6 m
c. 2.3E–7 m
d. 8.5E–7 m
a
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A single slit, 1,400 nm wide, forms a diffraction pattern when illuminated by monochromatic light of 490 nm wavelength. The largest angle from the central maximum at which the intensity is zero is closest to:
A) 44° B) 41° C) 38° D) 35° E) 32°
Three 2.50-?C charges are placed on tiny conducting spheres at the ends of 1.00 m-long strings that are connected at 120° angles as shown below. The magnitude, in N, of the force on the knot at the center is
?
?
A. 0. B. 3.75 × 10?2. C. 5.63 × 10?2. D. 6.50 × 10?2. E. 7.50 × 10?2.
If R = 3.0 k?, C = 6.0 nF, ?1 = 10.0 V, Q = 18 nC, ?2 = 6.0 V, and I = 5.0 mA, what is the potential difference Vb?Va?
A. ?13 V B. +28 V C. +13 V D. ?28 V E. +2.0 V
You can choose between a heat pump and an electric heater to heat your house. If you assume that the electric heater is 100% efficient at turning electrical energy into heat, an electric heat pump of what coefficient of performance (COP) will result in the same cost of electricity for the same amount of heating? Assume that the motor that runs the heat pump is 100% efficient
1.0.25 2.0.5 3.1.0 4.2.0