Quiz #2: 20 mins
1. A material will float on the surface of a liquid if the material has a
density less than that of a liquid. Given that the density of water is
approximately 1.0 g/mL, will a block of solid having a volume of 1.2 x 104
in3 and weighing 350 lb float or sink when replaced in a reservoir of
water? What is the density of the material?
1 in= 2.54 cm 1 mL= 1 cm3 1 kg= 2.2 lb = 1000 g
2. A small hole in the wing of a space shuttle requires a 20.7 cm2 patch.
What is the patch’s area in square kilometers (km2)? b) if the patching
material costs NASA $3.25/in2, what is the cost of the patch?
1 km= 1000 m
1 m= 100 cm
3. Suppose your dorm room is 11.8 ft wide by 12 ft long and 8.5 ft high
and has an air conditioner that exchanges air at a rate of 1200. L/min.
How long would it take the air conditioner (in min) to exchange the air in
your room once? How many times does your air conditioner completely
replace all the air in your in a day?
1 ft= 12 in
1 L= 1000 cm3
1. A material will float on the surface of a liquid if the material has a density
less than that of a liquid. Given that the density of water is approximately 1.0
g/mL, will a block of solid having a volume of 1.2 x 104 in3 and weighing 350 lb
float or sink when replaced in a reservoir of water? What is the density of the
material?
Solution:
Convert cubic inches to cubic centimeters, then to mL:
1.2 x 104 in3 = 196644.768 mL
Convert pounds to grams:
350 lb = 159090.9091 g
Calculate the density of the material and compare it to the density of water:
159090.9091 g / 196644.768 ml = 0.80902691 g/mL= 0.81 g/mL
Since this is less than the density of water, we conclude that the block of
material will float.
2. A small hole in the wing of a space shuttle requires a 20.7 cm2
patch. What is the patch’s area in square kilometers (km2)? b) if the
patching material costs NASA $3.25/in2, what is the cost of the patch?
It will cost $10.4.
3. Suppose your dorm room is 11.8 ft wide by 12 ft long and 8.5 ft high
and has an air conditioner that exchanges air at a rate of 1200. L/min.
How long would it take the air conditioner to exchange the air in your
room once? How many times does your air conditioner completely
replace all the air in your in a day?
It will take 26 min (28 min if 11.8 ft is plugged into the calculation) to
replace all the air in the room.
The AC replaces all the air in the room 54 times (51 times if 11.8 ft is
plugged into the calculation) in a day.