Two sacks contain the same number of identical apples and are separated by a distance r. the two sacks exert a gravitational force on each other that is opposite in direction but with the same magnitude, f. half the apples are removed from one sack and placed in the second sack. what is the magnitude of the gravitational force between the two sacks in terms of the original force, f?

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?