introductory physics calculating mass of water

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jaker904

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Feb 24, 2013
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ok heres my problem. im trying to calculate the mass of water with the following info

a cylindrical tank whose height is 9m and diameter 4.6m is completely filled with water

i figured i needed to calculate the volume first using the formula for calculating volume of a cylinder pi r h= p or density. the density of water being 1000kg/3
this is what i got.

radius= 4.6/2=2.3
3.14159 2.3 9=65.030913=volume

mass=V x P
= 65.030913 meters square x 1000kg/3
=65030.913 kgs

im way out of touch with my math and am basically teaching myself. i have no other resources and any feedback would be great thanks
 
jaker904 said:
ok heres my problem. im trying to calculate the mass of water with the following info

a cylindrical tank whose height is 9m and diameter 4.6m is completely filled with water

i figured i needed to calculate the volume first using the formula for calculating volume of a cylinder pi r h= p or density. the density of water being 1000kg/3
this is what i got.

radius= 4.6/2=2.3
3.14159 2.3 9=65.030913=volume .... volume of cylinder = \(\displaystyle \pi * r^2 * h \)

mass=V x P
= 65.030913 meters square x 1000kg/3
=65030.913 kgs

im way out of touch with my math and am basically teaching myself. i have no other resources and any feedback would be great thanks
Click to expand...

.
 
i cant do that using a standard calculator can i? im going to need a scientific calculator?
 
3.14159*2.3square*9=149.5710999=volume

mass=149.5710999*1000
mass=149571.0999kg
 
jaker904 said:
3.14159*2.3square*9=149.5710999=volume

mass=149.5710999*1000
mass=149571.0999kg
Click to expand...
I suggest (recommend, demand) that you put the units on every physical quantity - that will guide the calculations. [BTW, use "^" for raised to the power; ^2 means squared.]

V = pi (2.3 m )^2 (9 m) = 149.57 m^3, correct units for Volume.

m = rho*V = (1000 kg/m^3) (149.57 m^3) = 1.4957×10^5 kg, correct units for mass

Since the numbers given for r and h have very few significant figures, this should be rounded to 1.5×10^5 kg

A scientific calculator would include pi, and also scientific notation for powers of 10.
 
jaker904 said:
i cant do that using a standard calculator can i? im going to need a scientific calculator?
Click to expand...
If you have a microsoft computer, you probably have a scientific calculator on your desktop. Look under Accessories. Should be a calculator there. Bring it up. Hit the View tab in the top ribbon and click on scientific. Now you have a scientific calculator.
 
jaker904 said:
i cant do that using a standard calculator can i? im going to need a scientific calculator?
Click to expand...

You don’t need a scientific calculator to calculate the square of a number – just multiply the number by itself. On the other hand a scientific calculator would be useful if you wanted to do your calculations using \(\displaystyle \pi\) to more precision than just five decimal places.
 
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