Calculate the diameter of a parachute to be used for dropping an object of mass 100 kg so that the maximum terminal velocity of dropping is 5 m/s. The drag co-efficient for the parachute, which may be treated as hemispherical is 1.3. The density of air is 1.216 kg/m³.



Answer :

Answer:

The diameter of the parachute should be approximately 7.952 meters.

Step-by-step explanation:

To calculate the diameter of the parachute, we need to determine the area of the parachute required to achieve a terminal velocity of 5 m/s for an object with a mass of 100 kg. We will use the formula for terminal velocity which involves the drag force balancing the gravitational force.

[tex]/(The drag force/) \( F_d \) is given by:\[F_d = \frac{1}{2} C_d \rho A v^2\][/tex]

Where:

[tex]- \( C_d \) is the drag coefficient (1.3 for the parachute).\\- \( \rho \) is the density of air (1.216 kg/m^{3} ).\\- \( A \) is the area of the parachute.\\- \( v \) is the terminal velocity (5 m/s).[/tex]

The gravitational force [tex]\( F_g \)[/tex] acting on the object is:

[tex]\[F_g = mg\][/tex]

Where:

[tex]- \( m \) is the mass of the object (100 kg).\\- \( g \) is the acceleration due to gravity (9.8 m/s^{2} ).[/tex]

At terminal velocity, the drag force equals the gravitational force:

[tex]\[\frac{1}{2} C_d \rho A v^2 = mg\][/tex]

Solving for the area A:

[tex]\[A = \frac{2mg}{C_d \rho v^2}\][/tex]

Substituting the given values:

[tex]\[A = \frac{2 \times 100 \, \text{kg} \times 9.8 \, \text{m/s}^2}{1.3 \times 1.216 \, \text{kg/m}^3 \times (5 \, \text{m/s})^2}\][/tex]

[tex]\[A = \frac{1960 \, \text{kg} \cdot \text{m/s}^2}{1.3 \times 1.216 \times 25 \, \text{kg/m}^3 \cdot \text{m}^2/\text{s}^2}\][/tex]

[tex]\[A = \frac{1960}{39.52}\]\[A \approx 49.6 \, \text{m}^2\][/tex]

The parachute is hemispherical, so the area A corresponds to the flat circular base area of a hemisphere. The area of a circle is given by:

[tex]\[A = \pi r^2\][/tex]

Solving for the radius r:

[tex]\[r^2 = \frac{A}{\pi}\][/tex]

[tex]\[r = \sqrt{\frac{49.6}{\pi}}\]\[r \approx \sqrt{\frac{49.6}{3.1416}}\]\[r \approx \sqrt{15.8}\]\[r \approx 3.976 \, \text{m}\][/tex]

The diameter  D is twice the radius:

[tex]\[D = 2r\]\[D \approx 2 \times 3.976\]\[D \approx 7.952 \, \text{m}\][/tex]

Therefore, the diameter of the parachute should be approximately 7.952 meters.

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