12D Questions

[FabensMath]

Time to get serious with Calculator. I took this test today and scored a 254, didn't answer 7 and got 13 wrong(including the not answered).

So now I have questions and answers are greatly appreciated, Thanks!

12D-26. A CD is read at constant linear speed of 1.3m/s from the inside out, so its rotational velocity decreases during reading. If the readable area is between radii of 25 mm and 58 mm, what is the maximum difference in rotational velocity, a positive number? Answer: 283RPM

12D-37. Tracy can sew a Christmas ornament in 4 min, and Carol can sew on in 2.7 min. Starting at 8AM, TRacy works alone for time t and is then joined by Carol. What is t if they finished 120 ornaments at noon.
For this one i got up to something like x/2.4+x/4 = 120 -4t, but I don't know where to put the four hours.

12D-38. One thousand synchronized lights are placed in a line spaced 1ft apart. The first light flashes on/off, then after a time delay x, the second light flashes similarly, then the third, etc., such that the light blip "moves" along the row with constant velocity. What is x if the apparent blip velocity is 1.5 times teh speed of light, 186,000 mi/s? Answer:6.79*10^-4

I was doing (1000/5280)/(186000*1.5) = 6.78*10^-7seconds = .679micro seconds

12D-46. The specific surface area S of a particle is its total surface area divided by its mass. If a 200 micron sized particle had S = 1m^2/g, what size particle of identical shape has S = 50m^2/g? Answer: 4.00

12D-57. A parachutist deploys their parachute at a height of 3000ft, descending at a velocity of 5 ft/s above a point "X" on the ground. At the same time, a person starts running from Point X at an 8 minute mile. What is the closest distance between the two people? Answer: 2730
I think this one requires the Calculus applications, but I don't know too much Calculus, only basics, but I want to learn.

[88bobcat]

[88bobcat]