1) On a mountain biking trip, a group of riders had a big discussion about tire
ID: 1712479 • Letter: 1
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1) On a mountain biking trip, a group of riders had a big discussion about tire pressure. The most experienced rider in the group let out some air in his tires before the descent. Why would he want the tire pressure to be lower on the descent and higher during the climb? Explain in a few complete sentences. The air pressure in a bicycle tire is 32 psi on a typical winter day (40·F). Assuming the volume of air in the tire remains constant, find the pressure difference that occurs between a typical summer (80°F) and winter day. Discuss the forces that are responsible for supporting the tire and the bicycle when a rider is on the bicycle a. b. .Near the end of the ride, a rider noticed her bike tire was looking flat. The gage pressure read 10 psi. If the local atmospheric pressure is 12.6 psi, determine the absolute pressure in the tire. Report the answer in Pascals.Explanation / Answer
a) Since colder climates are associated with higher elevations and hotter climates with lower elevation, so when you are making a descent you are moving from a colder climate to a hotter climate. This means that since the temperature is rising on a descent, your tire pressure will also increase on a descent. So the expereinced rider was correct to lower the tire pressure, since it will eventually increase, since the volumne of air remains constant ( PV=nRT)
b) Pressure difference occurs at a typical rate of 1 psi for every 10 degree F so a chage of 40 degree F will cause a change of 4 psi .
c) The gare pressure is the defference between the atmospheric pressure and the tire pressure. Hence actual tire pressure is gage pressure + atmospheric pressue = 10 + 12.6 psi = 22.6 Psi
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