1. Try this while you wait:
A car goes 20. m ± 1 m in 2.0 s ± .2 s.
A) The speed is (20/2) = 10. m/s, but what is the uncertainty of the speed? (Calculate it as you did in the speed trap lab)
B) Express the fractional uncertainty of the distance in %. (i.e. what percent of 20m is 1 m?)
C) Express the fractional uncertainty of the time in %.
D) What is the fractional uncertainty of the speed in %
E) Notice anything?
A whiteboard measures 25 cm ± 2 cm by 45 ± 3 cm. The area is (25 cm)(45 cm) = 1125 cm2, but what is the uncertainty of the area? (You do it the same way as speed)

2. Try this while you wait:
A car goes 20. m ± 1 m in 2.0 s ± .2 s.
A) The speed is (20/2) = 10.0 m/s, but what is the uncertainty of the speed?
(10.0)(1/ /2) = 1.5 m/s, so it is 10.0 m/s ± 1.5 m/s
B) Express the fractional uncertainty of the distance in %. (i.e. what percent of 20m is 1 m)
well, it is 100x(1/20) = 5%
C) Express the fractional uncertainty of the time in %.
100x(.2/2) = 10%
D) What is the fractional uncertainty of the speed in %
100x(1.5/10) = 15%
E) Notice anything?
Yah – 5% + 10% = 15%
A whiteboard measures 25 cm ± 2 cm by 45 ± 3 cm. The area is (25 cm)(45 cm) = 1125 cm2, but what is the uncertainty of the area? (You do it the same way as speed)
(1125 cm2)(2/25 + 3/45) = 165 cm2 .:.