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Questions and Answers
What is pressure defined as?
What is pressure defined as?
- Force per unit area (correct)
- Mass per unit area
- Force per unit volume
- Force per unit mass
What is the unit of pressure in medicine?
What is the unit of pressure in medicine?
- Pa atm (correct)
- Atmosphere (atm)
- Pascal (Pa)
- Newton (N)
What causes atmospheric pressure?
What causes atmospheric pressure?
- Weight of the air in the atmosphere (correct)
- Weight of the water in the air
- Volume of the air in the atmosphere
- Temperature of the air
Which formula correctly represents pressure?
Which formula correctly represents pressure?
What is the atmospheric pressure in $N/m^2$?
What is the atmospheric pressure in $N/m^2$?
What is external work defined as?
What is external work defined as?
In the formula $ΔW = F Δx$, what does $Δx$ represent?
In the formula $ΔW = F Δx$, what does $Δx$ represent?
What condition must be met for external work to be done?
What condition must be met for external work to be done?
What is the formula for calculating the work done when climbing a hill?
What is the formula for calculating the work done when climbing a hill?
Which type of energy stored in the body is converted into external mechanical work?
Which type of energy stored in the body is converted into external mechanical work?
When a person is walking up stairs, what type of work is being done?
When a person is walking up stairs, what type of work is being done?
What is the unit of pressure measurement used in medicine?
What is the unit of pressure measurement used in medicine?
What is the peak systolic pressure in mm Hg?
What is the peak systolic pressure in mm Hg?
What is the density of mercury in $g/cm^3$?
What is the density of mercury in $g/cm^3$?
What does 1 Pascal (Pa) equal to?
What does 1 Pascal (Pa) equal to?
In which unit is pressure measured in the metric system?
In which unit is pressure measured in the metric system?
What is pressure defined as in a gas or liquid?
What is pressure defined as in a gas or liquid?
Which activity has the highest efficiency according to the table?
Which activity has the highest efficiency according to the table?
For long-term efforts, the body's performance is proportional to which factor?
For long-term efforts, the body's performance is proportional to which factor?
What is the efficiency of swimming underwater?
What is the efficiency of swimming underwater?
Which of the following phases can only last about a minute?
Which of the following phases can only last about a minute?
What does the body split to supply energy for short-term power needs?
What does the body split to supply energy for short-term power needs?
Which of the following is NOT listed as a related factor for oxygen consumption?
Which of the following is NOT listed as a related factor for oxygen consumption?
Which phase shows a rapid decrease in power produced with the duration of effort?
Which phase shows a rapid decrease in power produced with the duration of effort?
At what efficiency rate is shoveling performed?
At what efficiency rate is shoveling performed?
What is the formula for the pressure under a column of liquid?
What is the formula for the pressure under a column of liquid?
What is the acceleration due to gravity in cm/sec² when calculating pressure in Dy/cm²?
What is the acceleration due to gravity in cm/sec² when calculating pressure in Dy/cm²?
If the height of a column of water is 10 meters, what is the pressure in D/cm²?
If the height of a column of water is 10 meters, what is the pressure in D/cm²?
How do you calculate the pressure from a 12 cm column of mercury in Dy/cm²?
How do you calculate the pressure from a 12 cm column of mercury in Dy/cm²?
What height of water will produce the same pressure as 120 mm Hg?
What height of water will produce the same pressure as 120 mm Hg?
What is the pressure of 10 m of water when using N/m² as the unit?
What is the pressure of 10 m of water when using N/m² as the unit?
What primarily happens to the additional heat generated in muscles during exercise?
What primarily happens to the additional heat generated in muscles during exercise?
How is external work measured when a person rides a fixed bicycle?
How is external work measured when a person rides a fixed bicycle?
Which equation represents the efficiency (ε) of the human body?
Which equation represents the efficiency (ε) of the human body?
At what power level is the efficiency of the human body the lowest?
At what power level is the efficiency of the human body the lowest?
Which activity can increase the efficiency of the human body to 20%?
Which activity can increase the efficiency of the human body to 20%?
What is the formula for power (P) in terms of force (F) and velocity (V)?
What is the formula for power (P) in terms of force (F) and velocity (V)?
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Study Notes
Efficiency of the Human Body
- The efficiency of man for several activities is shown in the table, with an efficiency of around 20% for activities such as cycling and rowing.
- The maximum work capacity of the body is variable, with short-term efforts allowing for high power levels, but long-term efforts being more limited.
- The body uses anaerobic and aerobic phases to produce power, with anaerobic power decreasing rapidly with duration and aerobic power being constant.
Work and Power
- External work is defined as a force moved through a distance (Δx), and can be calculated as ΔW = F Δx.
- Power is the rate of doing work in time, and can be calculated as P = ΔW / Δt or P = FV, where V is velocity.
- The human body can be considered as a machine in doing external work, with efficiency calculated as the work done divided by the energy consumed.
Pressure
- Pressure is defined as the force per unit area in a gas or liquid, and can be calculated as P = F / A or P = mg / Lw.
- Atmospheric pressure is due to the weight of the air in the atmosphere, and is approximately 1.0 N/m².
- Units of pressure include Pascal (Pa), N/m², dynes/cm², and mmHg.
Measurement of Blood Pressure
- Blood pressure is a common phenomenon in our daily lives, and is typically measured by a doctor as part of a physical examination.
- Units of pressure in medicine include mmHg, with a typical systolic pressure being 120 mmHg.
- Pressure under a column of liquid can be calculated as P = pgh, where p is density, g is acceleration due to gravity, and h is height of the column.
Examples
- Example 1: Find the pressure of 10 m of water in Dy/cm² and N/m².
- P = pgh = 980000 = 9.8 x 10⁵ Dy/cm²
- P = pgh = 1000 x 9.8 x 10 = 9.8 x 10⁴ N/m²
- Example 2: Calculate the systolic pressure in Dy/cm² and N/m².
- P = p Hg g h Hg = 159936 = 1.6 x 10⁵ Dy/cm²
- P = p Hg g h Hg = 13600 x 9.8 x 0.12 = 1.6 x 10⁴ N/m²
- Example 3: What height of water will produce the same pressure as 120 mm Hg?
- P (120 mm Hg) = pgh = (13.6 g/cm³)(980 cm/sec²)(12 cm) = 1.6*10⁵ dyne/cm²
- h = 163 cm H2O.
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