This laboratory work explores the concept of Archimedes’ force as a pushing force that allows physical bodies to float on the surface of the water. The main criterion for determining the ability to float or sink is to compare the body’s density with the density of the liquid in which it is placed. Measured data are used to calculate the densities of three bodies, and answers are provided to explore the concept of density further.
First, the values of mass, width, and radius, as well as the gravity for the metal cylinder, were measured: the data are shown in Table 1. From the data, the volume of the cylinder can be calculated:
And the density of the cylinder:
The same can be calculated for the wooden block:
And for an irregularly shaped object:
Table 1: Measured values for metal cylinder, wooden block, and irregularly shaped object
|Metal Cylinder||Wood Block||Irregular Object|
|Mass, kg. (±0.01)||0.0277||0.0258||0.0661|
|Force, N. (±0.01)||0.2715||0.2531||0.6478|
|App. Weight, N.||0.1501||0.0098||0.4817|
|Sp. gravity to Water||2.72||0.42||8.27|
Based on these measurements and calculations, we can conclude that density is a more explanatory parameter because it has units of measurement and can be easily compared with the densities of other objects. The advantage of density over specific gravity is determined precisely by the unit of measurement: for example, for a block of wood, it can be found that one cubic meter of material contains 418.75 kg of wood, which cannot be detected from the specific gravity. The apparent change in weight is due to the ejection force – if the object was originally larger in volume, it pushes out more water. It follows that the ejection force for that body will be higher than the actual weight. In the context of density, we can conclude that the apparent weight will be less for bodies with higher density. For each fluid, the specific gravity values will be individual based on the nature of that parameter.
For the apparent weights of aluminum and iron, it is relevant that the higher-density material will have a lower apparent weight. The material appears more immersed in water when the apparent weight is greater. Visually (qualitatively), this will be observed as greater immersion of the material with greater density in the water. For the apparent weights of lead and aluminum, consider that lead has a significantly higher density than aluminum. Consequently, lead will have a greater mass for equal volumes, and when immersed in water, lead will be visually submerged in water more than aluminum. Consequently, the loss in weight will be greatest for the sample with the greater density, i.e., lead.
When the finger is submerged in the beaker of water, the number on the scale will be increased because the balance will be upset. The explanation is that the submerged finger displaces the water with a pushing force, which in turn causes the finger to exert an equilibrium force to remain stable in the liquid. The added force is what causes the weight on the scale to increase.
Compared to immersion in water, the change in mass for bodies immersed in the air is minimal due to the difference in densities. Indeed, a wooden block does not have an actual weight when immersed in the air because it pushes some of it out, but the change in accurate weight, in this case, is almost imperceptible.
The density of a body is related to temperature because the volume of the body and its temperature are related in direct proportion. As the temperature of the body increases, the volume expands, causing the density of the sample to decrease. However, this is true mainly for gases and liquids but not for solids, whose change in volume is negligible.
In this laboratory work, the physical concepts of pushing force based on studying the density of bodies were examined. The densities of three different bodies and their apparent weights were calculated. It explained what the decrease in apparent weight is related to, why some objects appear stronger than others immersed in a liquid, and how it depends on the density of the liquid.