A ping-pong ball covered with a conducting graphite coating has a mass of 2.5 × 10^-3 kg and a charge of 4.0 µC. What electric field directed upward will exactly balance the weight of the ball? (g = 9.8 m/s2)
a. 6.1 × 10^3 N/C
c. 5.1 × 10^6 N/C
b. 2.0 × 10^-7 N/C
d. 1.2 × 10^4 N/C
A
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