This is really more of a math problem, but I can't figure out what I'm doing wrong..."The standard kilogram is a platiunum-irridium cylinder 39.0 mm in height and 39.0 mm in dm. What is the density of the materia?"
Assuming that density is equal to mass/volume, I first calculated the volume of the cylinder, using the formula Volume=r^2(height)pi(19.5^2)(39)(pi)=46589 mm^3. I then divided 1kg by this number.
My answer was 2.15x10^-5 kg/m^3. However, the book says my answer should be 2.15 x 10^4 kg/m^3, which is obviously a big difference. Any help would be greatly appreciated!!
2007-06-04 14:30:44 · 8 answers · asked by Anonymous in Science & Mathematics ➔ Physics
1000 mm = 1 m
1000 000 000 mm³ = 1 m³
Notice that 4 - -5 = 9, which is how many zeros there are above. Put simply, you forgot to convert from mm to m.
2007-06-04 14:38:44 · answer #1 · answered by Boozer 4 · 1⤊ 0⤋
Your formula for volume was pi x r^2 x h. Did you use the radius 18.5mm, or did you use d=39mm. Also check your conversion from mm^3 to cubic meters. Probably you had the error there because you got the 2.15 right.
2007-06-04 14:42:00 · answer #2 · answered by morgan j 4 · 0⤊ 0⤋
Convert 39 mm to 39 x 10^(-3) m and solve this. You get the answer as it is in the book.
2007-06-04 14:41:06 · answer #3 · answered by Hell's Angel 3 · 0⤊ 0⤋
I get a volume calculation of 0.0000465889943025 m^3. Try converting your mm to m first, then running the calculation through. 19.5 mm = 0.0195 m, 39 mm = 0.039 m.
2007-06-04 14:41:08 · answer #4 · answered by Scott 2 · 0⤊ 0⤋
Seems to me that you got the volume in units of mm^3, when you should have used m^3.
Volume = pi * r^2 * H = pi * (0.019^2) * 0.039 = 4.659E-05 m^3
2007-06-04 14:43:25 · answer #5 · answered by morningfoxnorth 6 · 0⤊ 0⤋
You need to convert mm to meters. There are a thousand mm in a meter, so there are a billion cubic mm in a cubic meter. So your answer is off by a factor of 10^9,
2007-06-04 14:37:15 · answer #6 · answered by Anonymous · 1⤊ 1⤋
Check your units and make sure you used height and radius in meters not millimeters. I would suspect this is how you are off by a factor of 10^9.
2007-06-04 14:36:07 · answer #7 · answered by msi_cord 7 · 0⤊ 0⤋
Think of the rope as being two separate pieces with equal tension directed along the rope but away from the climber. Each piece exerts a vertical component of force of T sin(theta). Together they exert 2 T sin(theta). This balances the force of gravity, mg.
2016-05-21 08:00:08 · answer #8 · answered by anitra 3 · 0⤊ 0⤋