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 09-21-2005, 09:16 PM #1 Senior Member   Join Date: Aug 2004 Location: New York City Posts: 3,962 AP Physics Help! 6. According to a rule-of-thumb, every five seconds between a lightning flash and the following thunder gives the distance of the storm in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule. Reply
 09-21-2005, 09:34 PM #2 Senior Member   Join Date: Oct 2004 Posts: 1,592 That gives (1mi/5s)(1609m/mi)=321m/s Reply
 09-21-2005, 09:47 PM #3 Senior Member   Join Date: Aug 2004 Location: New York City Posts: 3,962 12. A bowling ball traveling with constant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.5 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s. Reply
 09-21-2005, 09:50 PM #4 Senior Member   Join Date: Oct 2004 Posts: 1,592 2.5=Ta+Tb, where Ta=time for ball to hit pins and Tb=time for sound of ball hitting to reach the bowler. d=vt, t=d/v, so Tb=16.5/340=.0485s. Ta=2.5-.0485=2.4515s. v=d/t=16.5/2.4515=6.73m/s I hope this isn't homework that you haven't even attempted.... Reply
 09-21-2005, 09:58 PM #5 Senior Member   Join Date: Aug 2004 Location: New York City Posts: 3,962 No it isn't homework. This is from my AP review book. I just didn't understand a few problems. Reply
 09-21-2005, 10:06 PM #6 Senior Member   Join Date: Oct 2004 Posts: 1,592 Ok...good...I'm surprised that anyone is doing AP review this early, however... Reply
 09-21-2005, 10:11 PM #7 Senior Member   Join Date: Aug 2004 Location: New York City Posts: 3,962 I have a quiz tomorrow in class about motion and stuff. I wanted more practice. Reply
 09-17-2008, 01:51 PM #8 New Member   Join Date: Sep 2008 Posts: 1 Calculate the average speed in m/s of a complete round-trip in which the outgoing 250 km is covered at 11.6 m/s followed by a 1.0-hour lunch break, and the return 250 km is covered at 17.2 m/s. how do u do this Reply
 09-18-2008, 02:35 AM #9 Senior Member   Join Date: Oct 2007 Location: SG -> SF Posts: 1,620 average speed = total distance / total time time for outgoing 250 km = 250 x 10^3 m / (11.6 m/s) = 21 551 s = 5.986 h time for break = 1 h time for return 250 km = 250 x 10^3 m / (17.2 m/s) = 14 534 s = 4.037 h total time = 11.02 h total distance = 500 km avg speed = 500/11.02 = 45.3 km/h = 12.6 m/s Reply

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