What other methods besides the water displacement method can you use to determine the density of a marble and a wire?

Answer 1

Water displacement, in and of itself, cannot be used to determine density. Density is defined as mass divided by volume. Water displacement determines only the volume part of density. Whatever method you use to determine volume, you still need to determine the mass of the item before you can calculate its density. That said, another way to determine the volume of an object is to measure its dimensions and apply the appropriate formula. A wire can be considered a cylinder. A very long and very thin cylinder, but a cylinder nonetheless. The formula for the volume of a cylinder is: V = lπr2 where l is the length of the cylinder, π is "pi", the ratio of a circle's circumference to its diamater, approximately 3.14159, and r is the radius of the cylinder, or half of its diameter. Simply use a ruler to measure the length of your wire. If it is bent, twisted, or kinked, you will need to straighten it out first. Instead of measuring the wire's radius, you should measure its diameter and divide by 2. Unless your wire is thick, it may be difficult to get an accurate measurement of its diameter, even in millimeter units. Instead, you might try cutting the wire into ten pieces and laying them all side by side, touching each other, then measure the total width of all then pieces, then divide by 20 to determine the radius of your wire. It is important that you use the same units for both length and radius of your wire. Once you have determined the length and radius of your wire, square the radius, then multiply it by 3.14159 (π), then multiply it by the length of the wire. That is your volume. If you measured your length and radius in millimeters, the volume will in cubic millimeters. A million cubic millimeters is equal to one liter, so if "liters" is the unit in the denominator of your density measurement, you will need to divide your "cubic millimeters" volume by 1,000,000 before computing density. A marble is a sphere. The volume of a sphere is determined by the formula: V = 4πr3/3 or V = πd3/6 where d is the diameter of the marble. To determine the diameter of your marble, place it on top of your ruler with the left side even with the zero mark, then measure where the right edge falls on your ruler. Again, this may not be very precise. Alternatively, you could make a mark on your marble, then place your marble on the ruler with the left edge at the zero mark and the mark in the exact center of the marble as viewed from above. Then roll the marble, one complete revolution, along the ruler, until the mark is again in the exact center, then measure where the left edge of the marble is again. This is the circumference of your marble. To determine its diameter, just divide by pi (3.14159). To determine the volume of your marble, multiply the diameter by itself, then by itself again (d x d x d, or d3), then multiply by pi (3.14159), then divide by six. This is the volume of your marble. If your diameter measurement was in millimeters, the volume will be in cubic millimeters.