Q:

hi
I have to design a hot air balloon.
I have started by estimating the weight. I have done this by using m = d x v
Can i check that this would be a correct way of calculating weight

- dave (age 15)

NY

- dave (age 15)

NY

A:

I guess you mean mass = density x volume.

That's true because it's the definition of density. The only thing you have to be careful about is that you don't screw up the units. If you want mass in kilograms, for instance, don't use density in pounds per cubic inch and volume in liters. The units of the density times the units of the volume ought to come out in the same mass (or weight) units that you want to use. Otherwise, you need to multiply by a units conversion factor.

Mike W.

That's true because it's the definition of density. The only thing you have to be careful about is that you don't screw up the units. If you want mass in kilograms, for instance, don't use density in pounds per cubic inch and volume in liters. The units of the density times the units of the volume ought to come out in the same mass (or weight) units that you want to use. Otherwise, you need to multiply by a units conversion factor.

Mike W.

*(published on 10/22/2007)*