Experiment Archimedes Principle

Objects of different sizes and shapes were measured with means of direct measurement, water displacement via submersion and with use of formula. Readings collected were then tabulated to calculate densities.

The densities of objects were calculated with two different methods. One of which was by direct measurement. The dimensions of the objects were measured with use of Vernier calipers, and masses of objects with use of a measuring balance. This method was only applied to objects with regular shapes. The densities obtained with direct measurements are:

a. Marble = 2.48 g/m­­3
b. Pendulum Bob = 8.44 g/m­­3
c. Magnet Bar = 4.59 g/m­­3

The density of objects was also measured with water displacement via submersion, in which the change in water volume denotes the volume of objects used. The values of object volume were then used to calculate the density of objects, and the densities calculated are:

a. Marble= 2.86 g/m­­3
b. Pendulum Bob= 7.57 g/m­­3
c. Magnet Bar= 4.26 g/m­­3
d. Small Nut= 7.97 g/m­­3
e. Big Nut= 7.26 g/m­­3

Of the two methods implemented to obtain the object densities, slight differences between results occurred (results iii). Such variation in results could be due to errors during experiment such as air bubbles trapped in the water container which would displace certain amount of water. Besides, instruments used would also give in chances errors, one of which was beam balance which was used to measure the mass of samples, can be easily affected by surroundings such as air movement, trembles on surface as well as calibration of the balance. Densities are also influenced by changes in temperature, hence the experiment should be conducted within a controlled environment.

Measurement via water displacement should be better used compared to direct measurements. Dimensions of certain objects are rather difficult to obtain, whilst water displacement method is available for both regular and irregular objects. The results from obtained from water displacement method will be used to determine of composition of samples.

Composition of materials:

a. Marbles
According to tables of specific gravity of common solids and metals, density of marble is 2.86 g/m3 and within errors, it falls between the range of glass specific density of 2.4 until 2.8 g/m3.

b. Pendulum Bob
The density of pendulum bob is 7.57 g/m3, according to the table of specific gravity the pendulum bob should be made of either Copper and Red Brass. The value was also close the specific gravity of lead but of it’s bronze coloured external lead is excluded from consideration.

c. Magnet Bar
The density of magnet bar is 4.26 g/m3, according to table of specific gravity it should be made of grey tin (5.75 g/m3).

d. Small Nut
The density of small nut is 7.97 g/m3 by which, according to table of specific gravity is made of zinc (theoretically 7.13 g/m3).

e. Big Nut
The density of Big nut is 7.26 g/m3, according to table of specific gravity is made of zinc (theoretically 7.13 g/m3).

According to Archimedes’s Principle, the net buoyant force is equal to the fluid displacement, therefore it was applied and verified in the calculation of density, where the measurement of volume of samples could be measured with the displacement of water during submersion. The Archimedes’s Principle also determine whether the sample used would sink or float in water. Objects sank during experiment should produce a specific gravity of greater than 1, contrary to this, objects would float if they produce a specific gravity lesser than 1.

For improved and more accurate results, measurement of sample masses should be conducted over an electronic balance instead of a beam balance for better precision level, the outcome should be more accurate as well since it’s less affected by environmental factors. During procedures involving water procedures, water should be poured slowly down the side of the container to avoid trapping air bubbles which would affect the reading of water volume. Apart from these, zero errors displayed by Vernier calipers are to be offset via calculation once detected. Objects that couldn’t be hanged by the string are to be placed gently into the container to avoid breakage of instrument as well.

Conclusion:

When an object is partially or fully submerged in a fluid, the magnitude of the buoyant force acting on the object equals to the weight of the fluid displaced by the object. Hence, the buoyant force is acting in an opposite direction to the weight of the object, as such the weight of an object submerged in a fluid is less than its weight in air. The difference between the weight of the object in air and the weight when it is submerged in a fluid equals to the buoyant force of the fluid acting on the object. For an object totally submerged in a fluid, the volume of the object equals to the volume of the displaced fluid. If the object is partially submerged, the volume of submerged part of the object only is equal to the volume of the displaced fluid.

References:
1) Acott, Chris (1999). “The diving “Law-ers”: A brief resume of their lives.” 2) Archimedes’s principle gets updated, R. Mark Wilson, Physics Today 65(9), 15 (2012) 3) “The works of Archimedes”. p. 257. Retrieved 11 March 2010. “