A typical car gas tank holds 15 gallons. (a) Calculate the energy content of this much gasoline. (b) calculate the chemical energy content of 15 gallons of hydrogen gas under normal atmospheric pressure (12.8 MJ/m3 as described under Equation 11.4), and compare your answer with the energy in the gasoline. Your answer shows why pressurizing, liquefying, or chemically combining hydrogen is necessary in hydrogen- powered vehicles.

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?