Experiment: Kinematics of Human Motion

Experiment 2: Kinematics of Human Motion
Laboratory Report

Mary Joyce M. Academia, Anawin M. Alcantara,
Anthea M. Allam, Celina Joyce C. Aniceto

Department of Biology
College of Science, University of Santo Tomas
Espana, Manila, Philippines

Abstract

        This experiment is divided into four activities namely, Graphical Analysis of Human Motion, Graph Matching, Graphical Analysis of Motion, and Reaction Time.

The Graphical Analysis of Human Motion yielded graphs showing the relationship of displacement versus time and velocity versus time in four different circumstances.

        The Graph Matching Activity allowed practical experience on how points on graph depicting kinematics actually means.

        The Graphical Analysis of Motion activity permitted us to compute for the average and instantaneous velocity, and analyze the motion done by one of our group mates.

        Lastly, the Reaction Time activity presented the relationship of time, distance and the acceleration due to gravity.

1. Introduction

        Kinematics is a branch of physics that involves defining motion without considering the masses and forces involved. It involves five variables - displacement, initial velocity, final velocity, acceleration and time.

        The objectives of this experiment are the following:

• To draw the displacement versus time graphs and velocity versus time graphs for uniform motion and uniformly accelerated motion
• To determine one’s normal reaction time and his reaction time while using his cellphone

        By the end of the experiment, the concept of kinematics as well as the relationship of the five aforementioned variables, through graphical analysis, would be better understood.

1. Theory

        This experiment was divided into three parts. The first and second part focused on the Graphical analysis of human motion and graph matching, wherein a Logger pro was used to detect motion of a certain object. LoggerPro is a general-purpose program for acquiring, graphing and analyzing data. It can accept input from a video camera, read a video file or, through the LabPro interface device, acquire data from a variety of other sensors. Pictorial data can be reduced to x-y coordinates of selected objects, while sensor data is presented in tabular form as a function of time. The program will prepare plots of the data, compute statistics like the mean, fit specified curves to a data series, and calculate derived quantities.

        The third activity wherein a person was asked to walk for ten seconds then distance travelled was recorded. The velocity was computed using the formula v=. Instantaneous velocity was also computed by multiplying the velocity by 2. iv=2v. [pic 1]

        Lastly, for the 4th activity we were asked to compute for the reaction time using the formula

[pic 2]

where it is defined as Reaction time. It is the interval time between the presentation of a stimulus and the initiation of the muscular response to that stimulus. A primary factor affecting a response is the number of possible stimuli, each requiring their own response, that are presented.

If there is only one possible response (simple reaction time) it will only take a short time to react. If there are several possible responses (choice reaction time) then it will take longer to determine which response to carry out.

Hick (1952) discovered that the reaction time increases proportionally to the number of possible responses until a point at which the response time remains constant despite the increases in possible responses (Hick's Law).

1. Methodology

        For the first activity of the second experiment, “Graphical Analysis of Human Motion,”. three graphs were sketched for displacement versus time and three graphs for  velocity versus time. The graphs were drawn based on the given movement and velocity of a person. The first person was moving away with constant velocity from a chosen starting point for a period of 10s. The second person was moving toward a chosen starting point with a constant velocity for a period of 10s. The third person was moving away from a chosen starting point along a straight line with increasing speed for a period of 10s.

        For the second activity, “Graph Making,” a member moved away from the Logger pro in such a way that the graph of her motion matched the position versus time graph ,and velocity versus time graph  on the computer screen.

[pic 3]

figure 1: a person moving away from the logger pro.

[pic 4][pic 5]

figure 2: graph of the motion made by a member of the group

For the third activity, “Graphical Analysis of Motion,” a group member walked in a straight line for 10s starting from rest. The distance travelled was then measured every second. The velocity and instantaneous velocity were computed after. Lastly, the data was graphed and analyzed.

        For the fourth activity, “Reaction Time,”  a group member was asked to hold the meter stick vertically at zero mark; while thumb and index finger were positioned at the 50 cm mark without touching the meter stick. The meter stick was then dropped by that  group member without telling about it, and was catched by another person using the thumb and the index finger. The reaction time of the rest of the members were also computed, and the procedure was repeated while calling a friend using cellphone.

figure 3: member 1 holding the 50 cm mark, member 2 getting ready to catch the ruler

IV. Results and Discussion                

A. Activity 1:         Graphical Analysis of                         HumanMotion

Graph 1: Displacement through Time of a Person Moving Away from the Origin (at Constant Velocity) [pic 6]

Graph 2: Velocity versus Time Through Time of a Person Moving Away from the Origin (at Constant Velocity) [pic 7]

Graph 3: Displacement through Time of a Person Moving Toward from the Starting Point (at Constant Velocity) [pic 8]