Question

Question 1 1 pts Formula sheet: Final Exam Formula Sheet.pdf A cubit is an ancient unit of length equal to 44 cm. A "jiffy" is a slang unit of time used in electronics equal to one period of alternating current, or 1/60th of a second. Convert a speed of 1 cubit per jiffy to km/hour. Question 2 1 pts Arunner completes a 5.120 km run in 38 minutes and 25 seconds. The uncertainty in distance is 3 m and the uncertainty in time is 5 seconds. What is the runners average speed with correct uncertainty? 2.2 +/- 0.1 m/s 2.22 +/-0.08 m/s 2.221+/0.001 m/s 2.221 +/-0.003 m/s 2.221 +/- 0.005 m/s 2.221 +/-0.007 m/s 2.2211 +/-0.0001 m/s

Answer 1

1) 1 cubit = 44 cm

1 jiffy =

S 60

Therefore,

$1\frac{cubit}{jiffy}=\frac{44cm}{\frac{1}{60}s}=\frac{44*10^{-5}km}{\frac{1}{60}*\frac{1}{60}*\frac{1}{60}h}=95.04km/hour$ [answer]

2) given:

s = distance = 5.120 km = 5120 m

uncertainty in distance = $\Delta s = 3m$

t = 38 minutes 25 seconds = (38*60)+25 = 2305 s

uncertainty in time = $\Delta t = 5s$

average speed = v = s/t = 5120/2305 = 2.221 m/s

for uncertainty calculation:

$\frac{\Delta v}{v}=\frac{\Delta s}{s}+\frac{\Delta t}{t}$

$\Rightarrow \Delta v=\left (\frac{\Delta s}{s}+\frac{\Delta t}{t} \right )*v$

$=\left (\frac{3}{5120}+\frac{5}{2305} \right )*\frac{5120}{2305}=0.00612m/s$ = 0.007 m/s (nearest value)

Therefore, the average speed with correct uncertainty is

2.221+/- 0.007 m/s [answer]