Correct answer only ! a car travels at a constant velocity of 70 mph for one hour. at the second hour, the car’s velocity was 60 mph. at the third hour, the car’s velocity was 80 mph. at what hour was their positive acceleration? at what hour was their negative acceleration? show your work!

Certain bacteria (such as aquaspirillum magnetotacticum) tend to swim toward the earth’s geographic north pole because they contain tiny particles, called magnetosomes, that are sensitive to a magnetic field. if a transmission line carrying 100 a is laid underwater, at what range of distances would the magnetic field from this line be great enough to interfere with the migration of these bacteria? (assume that a field less than 5% of the earth’s field would have little effect on the bacteria. take the earth’s field to be 5.0 * 10-5 t, and ignore the effects of the seawater.)