Linear air-resistance a hockey puck (m-0.1kg) slides across the ice (assume frictionless). however, there is linear air resistance, f=-bv, where b=5x10-5kg/s. the initial speed of the puck is 20 m/s. (a) (5 points) find the speed of the puck as a function of time. (b) (5 points) find the time where is the speed is half of the initial speed and distance travelled. (in radioactive decay, this time would be called the half-life) (c) (5 points) will the puck ever stop? is there a maximum distance travelled? if yes, what is that distance? (d) (15 points) now, include the effect of friction and let the coefficient of kinetic friction to be 0.1 and repeat (a) to (c).

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