Basic Physics help!?

Question

The Olypic record for the marathon is 2 h, 9 min, 21 s. The marathon distance is 26 mi, 385 yrd. Determine the average speed (in miles per hour) of the record.

I know that to find the average speed you divide distance by time. But I am confused as how to do it when i have hour min and seconds in my time,

I feel stupid, but I need help guys! :]

Answer 1

You must convert the elapsed time into one type of time for example

2h 9m 21s  = 7200 + 480 + 21 = 7701 seconds = 2.1392 hours  and the same with the distance convert it to all miles or all yards, so in this case  

26 mi , 385 yd = 26 + 385/1760= 26.2188 miles so the runners average speed is

26.2188 / 2.1392 = 12.26 m / hr

Answer 2

One hour = 3600 seconds, and one minute = 60s. So

2h + 9 min + 21s = 7200s + 540s + 21s = 7761s Divide this by 3600 to get the time in hours:

2587/1000 hours. 1 mile = 1760 yards, so 26 mi + 385 yrd = 26.21875.

Divide the distance by the time, or 26.21875 / (2587/1000) = 26.21875 * 1000/2587 = 10.135 miles per hour is the average speed.