WEBVTT
00:00:00.000 --> 00:00:03.160
This is Giancoli Answers
with Mr. Dychko.
00:00:03.800 --> 00:00:06.240
Percent uncertainty is calculated by
00:00:06.240 --> 00:00:08.900
dividing the absolute uncertainty
00:00:08.900 --> 00:00:12.500
which is the uncertainty in the same units
as your measurementâ€”
00:00:12.500 --> 00:00:15.420
0.2 seconds in this case is the
absolute uncertaintyâ€”
00:00:15.420 --> 00:00:18.720
divided by the measurement in part (a)
of 5.5 seconds
00:00:18.720 --> 00:00:21.300
and 0.2 divided by 5.5
00:00:21.300 --> 00:00:26.000
times a 100 to turn it into a percent
is 0.04 percent uncertainty.
00:00:26.400 --> 00:00:30.540
In part (b), it's 0.2 seconds divided by
55 seconds
00:00:30.680 --> 00:00:35.480
and this same uncertainty of 0.2 seconds
00:00:35.480 --> 00:00:39.240
should matter less when you have such a
long measurement of 55 seconds
00:00:39.240 --> 00:00:41.860
as compared to only 5.5 seconds
00:00:41.940 --> 00:00:43.880
and the percent uncertainty reflects that.
00:00:43.880 --> 00:00:46.160
So it's 0.004 percent
00:00:46.160 --> 00:00:50.380
uncertainty which is a much smaller percent
uncertainty than you had in part (a).
00:00:50.740 --> 00:00:54.560
In part (c), we are dividing by 5 minutes;
00:00:54.560 --> 00:00:56.500
now we have to make the units the same
00:00:56.560 --> 00:00:58.240
so on the denominator we have
00:00:58.240 --> 00:01:01.280
5 minutes times 60 seconds per minute
and the minutes cancel
00:01:01.280 --> 00:01:03.140
giving us this many seconds
00:01:03.140 --> 00:01:09.820
and this percent uncertainty is 6.7 times
10 to the minus 4 percent uncertainty.