Do It Yourself: Air Drag Force Experiment Using Paper and Scraper Sheet

Free fall motion in air medium is only influenced by gravitation acceleration. However, there are several variables that caused the observations to be different with the concept. Variables, such as air drag and terminal velocity, are often teachers not presented in detail, causing misconceptions. This study aims to develop a simple experiment on free fall motion by identifying air drag and terminal velocity. The data in this study is the video of free fall motion of paper and scraper analyzed using Tracker video analyze. From the video analyzed, information is obtained in the form of time (t), track (l, θ), and velocity (v) of the object. This study shows that the air drag force increase unto the terminal velocity. The calculation of the drag coefficient giving the number of the paper 2,16 and the scraper 2,10. According to data analyzed, the air drag force is affected by the mass (m), area (A), and the air drag force (F_D) with the linear correlation until it reaches the terminal velocity. The result of this study may use as references of free fall motion experiment with other objects and analyze.

Assessment of Selected Two-Phase Friction Multiplier Correlations for Steam-Water Flows in Vertical Heated and Unheated Tubes

In this study, around 10 000 experimental two-phase (2ϕ) flow pressure drop (ΔP) data for steam-water in uniformly heated and adiabatic vertical tubes have been compiled from the literature. The compiled data have been used to assess the prediction accuracy of two-phase friction multiplier (ϕlo2) correlations selected from the literature and the homogeneous-flow model for steam-water flow in vertical tubes. The predictions of the ϕlo2 correlations have also been compared to the predictions of the homogeneous-flow model. The assessments are based on comparisons of the average and the RMS errors. Additionally, ΔP components (due to gravitation, acceleration and friction) have been examined for a variety of flow conditions in vertical heated and unheated tubes. The results of the assessments show that the predictions of Muller-Steinhagen and Heck (1986) correlation yield the minimum RMS error for flow in heated tubes and the predictions of the Chisholm (1973) correlation yield the minimum RMS error for flow in adiabatic tubes when these predictions are compared with both the data base and the predictions of the homogeneous-flow model. It is concluded from the research and a review of the literature that the current state of the art is such that none of the investigated prediction methods is very good because of their large RMS errors. More work is needed to expand the ΔP data base especially for adiabatic two-phase flow. Also, a systematic experimental study should be performed on the effect of heating on the 2ϕ-flow ΔP.