Auniform ladder is 10 m long and weighs 400 n. it rests with its upper end against a frictionless vertical wall. its lower end rests on the ground and is prevented from slipping by a peg driven into the ground. the ladder makes a 30◦ angle with the horizontal. the magnitude of the force exerted on the peg by the ladder is:

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?