Question 112 of 949
The hydrostatic blood pressure difference between the head and the feet of a boy standing straight is 1.65 x 104 Nm-2. Find the height of the boy.
[ Density of blood = 1.1 x 103 kgm-3, g = 10ms-2]
- A. 0.5 m
- B. 0.6 m
- C. 1.5 m
- D. 2.0 m
Correct Answer:
C
Explanation
To solve the problem of finding the height of the boy based on the hydrostatic blood pressure difference, we can use the hydrostatic pressure formula. Let's break down the steps clearly.
### Step 1: Understand the Hydrostatic Pressure Formula
The hydrostatic pressure difference (\( \Delta P \)) between two points in a fluid column is given by the formula:
\[
\Delta P = \rho g h
\]
Where:
- \( \Delta P \) = pressure difference (in Pascals, or \( \text{N/m}^2 \))
- \( \rho \) = density of the fluid (in \( \text{kg/m}^3 \))
- \( g \) = acceleration due to gravity (in \( \text{m/s}^2 \))
- \( h \) = height difference (in meters)
### Step 2: Identify the Given Values
From the problem, we have:
- \( \Delta P = 1.65 \times 10^4 \, \text{N/m}^2 \)
- \( \rho = 1.1 \times 10^3 \, \text{kg/m}^3 \)
- \( g = 10 \, \text{m/s}^2 \)
### Step 3: Rearranging the Formula
We need to find the height \( h \). Rearranging the hydrostatic pressure formula gives us:
\[
h = \frac{\Delta P}{\rho g}
\]
### Step 4: Substitute the Values
Now, we can substitute the known values into the rearranged formula:
\[
h = \frac{1.65 \times 10^4 \, \text{N/m}^2}{(1.1 \times 10^3 \, \text{kg/m}^3)(10 \, \text{m/s}^2)}
\]
### Step 5: Calculate the Denominator
First, calculate the denominator:
\[
\rho g = (1.1 \times 10^3 \, \text{kg/m}^3)(10 \, \text{m/s}^2) = 1.1 \times 10^4 \, \text{N/m}^3
\]
### Step 6: Calculate the Height
Now substitute this back into the equation for \( h \):
\[
h = \frac{1.65 \times 10^4 \, \text{N/m}^2}{1.1 \times 10^4 \, \text{N/m}^3}
\]
Calculating this gives:
\[
h = \frac{1.65}{1.1} \, \text{m} = 1.5 \, \text{m}
\]
### Conclusion
Thus, the height of the boy is **1.5 m**. Therefore, the correct option is **C**.
### Explanation of Other Options
- **Option A (0.5 m)**: This is too low for the height calculated based on the pressure difference. It does not satisfy the hydrostatic pressure equation.
- **Option B (0.6 m)**: Similar to option A, this value is also too low and does not match the calculated height.
- **Option D (2.0 m)**: This value is higher than the calculated height. It would imply a greater pressure difference than what is given.
### Revision Summary
- The hydrostatic pressure difference can be calculated using \( \Delta P = \rho g h \).
- Rearranging gives \( h = \frac{\Delta P}{\rho g} \).
- Substitute the known values carefully to find the height.
- The correct height of the boy is **1.5 m**, corresponding to option **C**.