Hidrostática - Aula 03 (Densidade e Massa Específica)

Summary

This video provides a clear and detailed explanation of how to calculate density and specific mass. It covers key concepts like the formula for density (mass/volume), demonstrating how to apply it with various examples. The video explains the importance of unit conversions, such as from liters to cubic centimeters, and emphasizes the significance of considering only the solid part of an object when calculating specific mass. With practical examples, the video makes understanding these concepts easy for learners in science and engineering.

Takeaways

• 😀 Density is the ratio of mass to volume, and the formula used is Density = Mass / Volume.
• 😀 When calculating density, be sure to exclude the volume of any empty or void spaces in the object.
• 😀 Specific mass refers to the mass of only the solid (massy) part of the object, not including any hollow areas.
• 😀 In an example, a body with a total volume of 50 cm³ and 10 cm³ of empty space has a mass-specific volume of 40 cm³.
• 😀 To calculate the density in this scenario, the formula becomes Density = Mass / 40 cm³, resulting in a density of 2.5 g/cm³.
• 😀 To calculate the mass of an object when density and volume are known, use the formula: Mass = Density × Volume.
• 😀 In one example, a volume of 50 cm³ and a density of 2 g/cm³ gives a mass of 100 grams.
• 😀 Conversions are crucial when different units are involved. For example, converting liters to cubic centimeters is necessary when dealing with liquids.
• 😀 When the density is given in grams per cubic centimeter (g/cm³) and the volume is in liters, the density can be converted to kilograms per liter (kg/L) for ease of calculation.
• 😀 For instance, if the density of oil is 0.92 g/cm³, it is equivalent to 0.92 kg/L when working with liters, simplifying calculations.
• 😀 In another example, calculating the mass of 2 liters of oil with a density of 0.92 kg/L results in a mass of 1.84 kilograms.

Q & A

What is the formula for calculating density?

The formula for calculating density is: density = mass / volume.

What units are typically used to measure density in this context?

In this context, density is typically measured in grams per cubic centimeter (g/cm³) or kilograms per liter (kg/L).

How is density calculated if you have the mass and volume?

To calculate density, you divide the mass of an object by its volume. For example, if the mass is 100 grams and the volume is 50 cm³, the density would be 100 g / 50 cm³ = 2 g/cm³.

What should you do when you have a volume in liters and density in grams per cubic centimeter?

You need to convert the volume from liters to cubic centimeters because 1 liter equals 1000 cubic centimeters. Once converted, you can use the density formula to calculate the mass.

In the example with a 50 cm³ volume and 2 g/cm³ density, what is the mass of the object?

The mass of the object would be calculated as: mass = 2 g/cm³ × 50 cm³ = 100 grams.

How do you calculate the specific mass (or specific gravity) of an object?

To calculate the specific mass (or specific gravity), you must first determine the volume of only the solid, or 'massy' part of the object, excluding any voids. Then, use the formula: mass / volume.

Why is it important to exclude the hollow parts of an object when calculating its specific mass?

Excluding the hollow parts is important because specific mass refers to the mass of the solid material in the object, and hollow parts do not contribute to the mass of the object.

In the case where the volume of an object is 50 cm³ and 10 cm³ is hollow, what volume should be used for the calculation of specific mass?

For the calculation of specific mass, you should subtract the volume of the hollow part from the total volume. If the total volume is 50 cm³ and the hollow part is 10 cm³, the volume to use would be 40 cm³.

How do you calculate the mass of a substance if you are given the volume in liters and the density in grams per cubic centimeter?

To calculate the mass, convert the volume from liters to cubic centimeters (1 liter = 1000 cm³), and then use the formula: mass = density × volume. For example, if the density is 0.92 g/cm³ and the volume is 2 liters, the mass would be 0.92 g/cm³ × 2000 cm³ = 1840 grams or 1.84 kilograms.

What is the relationship between density in grams per cubic centimeter and density in kilograms per liter?

The relationship is that 1 g/cm³ is equivalent to 1 kg/L. This means that the density values are numerically the same in both units, but the unit names differ (grams vs. kilograms and cubic centimeters vs. liters).