Zachary

A box contains 10 balls numbered 1, 2, . . ., 10. Suppose that two balls are selected at

random without replacement from this box and the numbers on the balls are noted. Find

the probability that the numbers on the two balls differ by 2 or more.

Redo the problem above assuming that the two balls are selected with replacement.

I have a feeling I'm close to an answer for the first question but the "or more" part of it concerns me.

(9-2)/(10 choose 2) is what I have so far.

An electric charge q1 (-6e) is located at the origin. A second electric charge q2 (+2e) is located a distance "d" from the origin. In terms of "d", what is the distance "x" from q1 where the net electric potential is zero? Assume for this problem that x<d. I imagine you need to use V = kq/r. Please provide an explanation.

An electric charge q1 (-6e) is located at the origin. A second electric charge q2 (+2e) is located a distance "d" from the origin. In terms of "d", what is the distance "x" from q1 where the net electric potential is zero? Assume for this problem that x<d. I imagine you need to use V = kq/r.

An electric charge q1 (-e) is located at the origin. A second electric charge q2 (-4e) is located at a distance d from the origin on the x-axis. A third charge q3 (+e) is located a distance x, which is less than d, on the x-axis between q1 and q2. In terms of d, what is the distance x where the net electric force is zero?

from Earth and its diameter is opposite and angle of 32' relative to an observer on Earth, what is the diameter of the sun?