A 0.500-kg object rests on a horizontal frictionless surface. It is in a position such that it is compressing a spring a distance 12.0 cm. If the object is released, the object leaves the
spring at a speed of 20.0 cm/s. What is the spring constant of the spring?

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?