Still considering the system of the comet plus the star, which of the following statements are correct? a. the sum of the kinetic energy of the system plus the gravitational potential energy of the system is a positive number. b. along this path the gravitational potential energy of the system is never zero. c. the gravitational potential energy of the system is inversely proportional to the square of the distance between the comet and star. d. at every location along the comet's path the gravitational potential energy of the system is negative. e. the sum of the kinetic energy of the system plus the gravitational potential energy of the system is the same at every location along this path.

Why is alternating current more effective at long–distance travel than direct current? a. the power lines are made out of conductors. b. transformers increase or decrease voltage as needed. c. the ac generator is more efficient. d. ac has lower voltage than dc.

What is the length x of the side of the triangle below? (hint: use the cosine function)

In the future, people will only enjoy one sport: electrodisc. in this sport, you gain points when you cause metallic discs hovering on a field to exchange charge. you are an electrodisc player playing the popular four disc variant. the disks have charges of qa = −8.0 µc, qb = −2.0 µc, qc = +5.0 µc, and qd = +12.0 µc. (1) you bring two disks together and then separate them. you measure the resulting charge of these two disks and find that it is +5.0 µc per disk. which two disks did you bring together? (a) a and b (b) a and c (c)a and d (d)b and c(e) b and d (f) c and d. (2) you bring three disks together and then separate them. you measure the resulting charge of these three disks and find that it is +3.0 µc per disk. which three disks did you bring together? a, b, and c (a) a, b, and d (c) a, c, and d (d) b, c, and d. (3) given the resulting charge of each disk measured in (b) is +3.0 µc, how many electrons would you need to add to a disk of this charge to electrically neutralize it? electrons