18. In an airplane flying at a constant speed, the
force pushing the airplane forward is exerted
by the engine and is equal to the opposite
force of air resistance. Describe how these
forces compare when the plane speeds up
and slows down. In which direction is the
net force on the airplane in each case?

You have two photos of a person walking. one shows the person at the corner of third and main streets, the other shows the person at the corner of tenth and main streets. there are lampposts at every corner in this town, and the first picture shows it to be 10: 32: 00 exactly. the second picture shows it to be 10: 49: 30. you know three facts: (1) all of the clocks are synchronized; (2) there are exactly 12 equal-sized blocks per kilometer in this town; and (3) the streets that cross main in this area are numbered consecutively, with no interruptions. what is the person’s average speed in kilometers per hour?