Three point charges, two positive and one negative, each having a magnitude of 20 ?C are placed at the vertices of an equilateral triangle (30 cm on a side). What is the magnitude of the electrostatic force on the negative charge?
a. 80 N
b. 40 N
c. 69 N
d. 57 N
e. 75 N
c
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A wire (length = 2.0 m, diameter = 1.0 mm) has a resistance of 0.45?. What is the resistivity of the material used to make the wire?
a. 5.6 × 10^?7 ? / m b. 1.2 × 10^?7 ? / m c. 1.8 × 10^?7 ? / m d. 2.3 × 10^?7 ? / m e. 7.1 × 10^?7 ? / m
If y = 0.02 sin (30x - 400t) (SI units), the velocity of the wave is
a. 3/40 m/s b. 40/3 m/s c. 60p/400 m/s d. 400/60p m/s e. 400 m/s
Where was supernova 1987a located?
A) in the Orion Nebula, M-42 B) in Sagittarius, near the Galactic Nucleus C) in our companion galaxy, the Large Magellanic Cloud D) in M-13, one of the closest of the evolved globular clusters E) near the core of M-31, the Andromeda Galaxy
A string on a guitar is stretched between two points 35.0 cm apart with a tension of 65.0 N. The mass/length of the string is 0.00400 kg/m. The wavelength of the mode of vibration with the lowest frequency is
A. 0.5 m. B. 0.6 m. C. 0.7 m. D. 0.8 m. E. 0.9 m.