This is Giancoli Answers with Mr. Dychko. The sprinter's acceleration is the change in their velocity divided by time so that's final velocity of 9 meters per second minus initial velocity of zero. So we have 9 divided by 1.38 seconds which is 6.52 meters per second squared. In part (b), we can convert that into kilometers per hour squared by multiplying this meters per second squared by 3600 seconds for every hour all squared that gives us seconds squared here canceling with this second squared here and then we have hours squared on the bottom and then we multiply by 1 kilometer for every 1000 meters giving us 8.45 times 10 to the 4 kilometers per hour squared. So every hour, the speed of the sprinter would change by 8.45 times 10 to the 4 kilometers per hour.
Hello, why do we have to square the 3600?