A charge of +3.0 mC is distributed uniformly along the circumference of a circle with a radius of 20 cm. How much external energy is required to bring a charge of 25mC from infinity to the center of the circle?
a. 5.4 J
b. 3.4 J
c. 4.3 J
d. 2.7 J
e. 6.8 J
B
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When four hydrogen are fused to make one helium nuclei, a small amount of matter is converted into what?
a. photons b. other matter c. energy d. gamma rays, neutrinos, and positrons
Index of Refraction: The index of refraction of a certain glass is measured to be 1.5. What is the speed of light in that glass? (c = 3.0 × 108 m/s)
A. 1.0 × 108 m/s B. 2.0 × 108 m/s C. 3.0 × 108 m/s D. 4.0 × 108 m/s E. 5.0 × 108 m/s
Why are sunsets and sunrises red?
What will be an ideal response?
A set of twins, Andrea and Courtney, are initially 10 years old. While Courtney remains on Earth, Andrea rides on a spaceship which travels away from Earth at a speed of 0.60c for five years (as measured by Courtney),
then immediately turns around and comes back at 0.60c. When Andrea returns, Courtney is 20 years old. How old is Andrea upon her return? A) 20 y B) 12 y C) 10 y D) 15 y E) 18 y