Posted: 11/22/2007 2:13:34 PM EDT
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Trying to help my son with a science project, and without going into a lengthy explanation I'm trying figure out the following: if an object travels 7' 6" in the following times, how can I determine the miles per hour. 1.219 seconds 1.078 seconds 0.894 seconds I listed the times in case it's easier than trying to splain it. Thanks. |
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conversion of units is your friend... Convert the feet to miles, then the seconds to hours... use this for the long math - http://www.onlineconversion.com/ can't hot link it...MIL web is the sucks OK...edited to add a little more info: To do it more easily you will need to use algebra. Convert all times to even ratios of the distance...ie 7.5ft/1.219sec = 6.15ft/sec now we have a easy number to work with. from the calculator listed above: 6.15 foot/second = 4.193 181 818 mile/hour (mph) you can do this with units too: 1 foot/second = 0.682 mile/hour |
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1 Mile = 5280 Feet = 63360 Inches 7'6" = 90" Working on the rest... (at work and can't get locked into the PC)  ETA - I may be going on the completely wrong path but FWIW: 63360 (1 MI in inches) is divisible by 90 and results in 704. 1.219 x 704 = 858 1.078 x 704 = 758.912 0.894 x 704 = 629.376 |
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This is easy if you think about the units. You have a time and a distance, and you want to get a speed. Speed is time/distance. Then you just have to go from feet/second into miles per hour so just multiply by the correct ratios like this: feet / seconds * seconds / hour * miles / feet for example: 7.5 feet / 1.219 seconds * 3600 seconds / 1 hour * 1 mile / 5280 feet the seconds and the feet cancel out, leaving you with miles / hour. If your son is interested in science and/or engineering, teaching him to think about units at an early age will be invaluable to him. |