Transcript Dimensional Analysis Practice Answers II.pptx

1. How many seconds are in 3.5 years? 2 points)
60 sec 60 mins 24 hrs 365 days = 31,536,000 secs
1 min
1 hr
1 day
1 year
1 year
31,526,000=3.15 x 107 x 3.5=11.03 or 1.10 x 108 secs
1 year
3.5 years
Or 110,376,000 secs
3.5 years
2. Battery electric vehicles (BEVs) have been introduced to
consumers as an alternative way to reduce the
environmental effects caused by use of internalcombustion engine (ICE) vehicles. A comparison of both
vehicle types can help determine whether the use of BEVs
would be beneficial in the future.
(A)Assume that the fuel efficiency of the ICE vehicle is 25
miles per gallon (mpg) and that gasoline costs $3.75 per
gallon (gal). Calculate the cost of gasoline per mile. (2
points)
$3.75
gal
1 gal
25 mi
$3.75
25 mi
=
$0.15
1 mi
2. (B) The charger supplies energy to the BEV battery at an
average rate of 4.0 kilowatts (kW)/hour, and fully charges the
BEV battery in 7.0 hours. The car will run for 100 miles on a
full charge. The cost of electricity is $0.11 per kilowatt-hour
(kWh).
i. Calculate the cost of the electricity to fully charge
the battery. Assume that the battery is not charged to begin
with (2 points).
4 kW
1 hr
7 hr
$0.11
kWh
= $3.08
ii. Calculate the cost of electricity per mile to drive the
BEV. (2 points)
$3.08
100 mi
= $0.03/mile
When it is driven 100 miles, the ICE vehicle contributes 72.8
pounds (lbs) of CO2 to the atmosphere from the combustion of
the gasoline. The drilling, refining, and transportation costs of
getting the gasoline to the gas station add an additional 17.7
lbs of CO2 per 100 miles. The BEV does not emit any CO2
itself, but the extraction, transportation, and combustion of
the coal that produces the electricity at the power plant adds
63.6 lbs of CO2 for the same 100 miles.
(C) Calculate the difference in the amount of CO2 that would
enter the atmosphere if both cars were driven 100 miles.
(2 points)
ICE = 72.8 lbs. + 17.7 lbs. = 90.5 lbs CO2
BEV= 63.6
Difference = 90.5 lbs – 63.6 lbs = 26.9 lbs CO2