hC.9
Introduction
Anthropometry takes into consideration the physical human traits applied to determine the allowable space, equipment shape and size to be used in undertaking tasks. Factors such as agility and mobility, body size, age, sex, strength and disabilities are considered. Engineering anthropometry relates such data to workplaces, equipment, tools, chairs as well as other consumer products. The ultimate goal is create a workplace that is not only efficient and safe, but also comfortable for the user (Bridger 86). Owing to the fact that is impossible to satisfy all the varied range of body sizes in the worker/user population, anthropometric data is applied to accommodate for 90 to 95 percent of the body sizes of people.
Part 1
The size of the user’s hand is a key consideration in the design of controls such as cutlery (e.g knife). Thus in designing a knife, key hand dimensions must be addressed. These include: the maximum grip, the breadth of the hand, the circumference of the hand, and the circumference of the wrist.
Figure 1: The key hand dimensions
The equipment of choice for this exercise is the Chicago Cutlery Centurion 8-Inch Chef’s Knife. Its dimensions are 3x1x16 inches; 11.8 ounches.
Figure 1: Chicago Cutlery Centurion 8-Inch Chef’s Knife
The Chicago Cutlery Centurion 8-Inch Chef’s Knife is not only very efficient, sharp, and comfortable to use, but is also tailored to suit the body size of the user. The knife’s blade are made of extra-thick, stamped high-carbon stainless steel along with triple compression stainless steel rivets that offer balance, strength and safety to the user. The Chicago Cutlery Centurion 8-Inch Chef’s Knife is perfect for beginner cooks searching for simple cutting solutions at daily value because the ergonomic handle is perfectly balanced to allow for safe tireless use.
Part 2: technique for measuring height
Day/Time Evening (before sleep) Morning (after waking)
Day 1 169cm 170cm
Day 2 169cm 171cm
Day 3 169cm 170cm
The average morning height is 170cm while it is 169cm at night. This translates that the height decreases between 1cm or 2cm during in the course of the day. In other words, the % change of the height is a negative quantity.
% change = (evening average height – morning average height) x 100
Morning average height
% change = [(169-170)/170] x 100
% change = 0.588%
The decrease in height was nearly -0.6% each day of the three measurement days. The negative change experienced during the day is offset by a positive change recorded at night meaning that the height only increased at night. Thus height is a variable quantity – an individual is slightly, but measurably, taller in the morning when they wake up than at the end of the day when they retire to bed. This is because during the day when am standing, sitting or walking (i.e. in a vertical position), the force of gravity acts to compress the spine (Bridger 86). However, the Earth’s gravity does not act to compress the spine when we are lying down (i.e. in a horizontal position) at night, which makes it able to stretch and lengthen. As a result we are an inch or two taller when we wake up in the morning than at early evening when we retire to bed.
Part 3
Ct = (Force due to body weight + Force due to load) * cosine angle of flexion
+ (Compression due to back muscle force needed to maintain posture)
Therefore; to maintained an equilibrium
Sum of Clockwise Forces = Sum of Anti Clockwise Forces
Sum of Clockwise Forces = (Force due to body weight + Force due to load) * cosine angle of flexion
= (300 + 100) cos 0 50
= 2000 Ncm
Sum of Anti Clockwise Forces = Compression due to back muscle force needed to maintain posture
= (Force generated by erector spine muscles) x (5cm)
Since Sum of Clockwise Forces = Sum of Anti Clockwise Forces
Therefore
2000 Ncm = Force generated by erector spine muscles x (5cm)
2000Ncm/ 5cm= Force generated by erector spine muscles
=400Ncm
The total compressive force is equal Sum of Clockwise Forces +Sum of Anti Clockwise Forces
= (2000 + 400)
=2400Ncm
b) Depending on the position of the load in compared to the joint or fulcrum, muscles and bones give either a mechanical advantage or mechanical disadvantage when lifting an object. Therefore, the nearer the load to the fulcrum and the farther the effort (muscle), the easier it is to lift the given object (Bridger 60). On the other hand, the more distant the load is from the fulcrum and closer the effort is to the fulcrum, the harder it is to lift the object. In this case, therefore:
MA = length of effort arm/length of load arm = 5cm/50cm = 0.1
Part 4
Calculating mean and standard deviation
To calculate the standard deviation, you first determine the mean of the numbers givens. Then, subtract the mean from every single number to reach the list of deviations. Thereafter, square the resulting list of numbers (i.e. multiply them with themselves). The standard deviation is reached by finding the square root of the resulting number.
Therefore, the standard deviation for 1,3,3,5 calculated as:
Where
σ = standard deviation
xi = each value of dataset
x (with a bar over it) = the arithmetic mean of the data
N = the total number of data points
∑ (xi – mean)2 = The sum of (xi – mean)2 for all data points
Calculate the mean:
= 1+3+3+5 = 3
4
Then:
(1-3)2=4
(3-3)2=0 = 4+0+0+4 = 8
(3-3) 2=0
(5-3)2=4
Standard deviation = √[8/(4-1)] = 1.63299
URL online calculator: http://easycalculation.com/statistics/standard-deviation.php
References:
Bridger. S. R. Introduction to Ergonomics: Instructor’s Manual. New York: Taylor & Francis, 2003.
