1. A sphere with a mass of 10 kg and radius of 0.5 m moves in free fall at sea level (where the air density is 1.22 kg/m3). If the object has a drag coefficient of 0.8, what is the object’s terminal velocity? What is the terminal velocity at an altitude of 5,000 m, where the air density is 0.736 kg/m3? Show all calculations in your answer.

Respuesta :

Answer:

The terminal velocity at sea level is 7.99 m/s

The terminal velocity at an altitude of 5000 m is 10.298 m/s

Explanation:

mass of sphere m  = 10 kg

radius of sphere r = 0.5 m

air density at sea level p = 1.22 kg/m^3

drag coefficient Cd = 0.8

terminal velocity = ?

Area of the sphere A = [tex]4\pi r^{2}[/tex] = 4 x 3.142 x [tex]0.5^{2}[/tex] = 3.142 m^2

terminal velocity is gotten from the relationship

[tex]Vt = \sqrt{\frac{2mg}{pACd} }[/tex]

where g = acceleration due to gravity = 9.81 m/s^2

imputing values into the equation

[tex]Vt = \sqrt{\frac{2*10*9.81}{1.22*3.142*0.8} }[/tex] = 7.99 m/s

If  at an altitude of  5000 m where air density = 0.736 kg/m^3, then we replace value of air density in the relationship as 0.736 kg/m^3

[tex]Vt = \sqrt{\frac{2mg}{pACd} }[/tex]

[tex]Vt = \sqrt{\frac{2*10*9.81}{0.736*3.142*0.8} }[/tex] = 10.298 m/s

The value of terminal velocity of object is 7.99 m/s and the value of terminal velocity at an altitude of 5000 m is 10.30 m/s.

Given data:

The mass of sphere is, m = 10 kg.

The radius of sphere is, r = 0.5 m.

The density of air is, [tex]\rho = 1.22 \;\rm kg/m^{3}[/tex].

The drag coefficient of object is, [tex]C_{d}=0.8[/tex].

The altitude is, h = 5000 m.

The density of air at altitude is, [tex]\rho' =0.736 \;\rm kg/m^{3}[/tex].

The mathematical expression for the terminal velocity of an object is,

[tex]v_{t}=\sqrt\dfrac{2mg}{\rho \times A \times C_{d}}[/tex]

here,

g is the gravitational acceleration.

A is the area of sphere.

Solving as,

[tex]v_{t}=\sqrt{\dfrac{2 \times 10 \times 9.8}{1.22 \times (4 \pi r^{2}) \times C_{d}}}\\\\\\v_{t}=\sqrt{\dfrac{2 \times 10 \times 9.8}{1.22 \times (4 \pi \times 0.5^{2}) \times 0.8}}\\\\\\\v_{t}=7.99 \;\rm m/s[/tex]

Now, the terminal velocity at the altitude of 5000 m is given as,

[tex]v_{t}'=\sqrt\dfrac{2mg}{\rho' \times A \times C_{d}}[/tex]

Solving as,

[tex]v_{t}'=\sqrt{\dfrac{2 \times 10 \times 9.8}{0.736 \times (4 \pi \times 0.5^{2}) \times 0.8}}\\\\\\v_{t}'=10.30 \;\rm m/s[/tex]

Thus, we can conclude that the value of terminal velocity of object is 7.99 m/s and the value of terminal velocity at an altitude of 5000 m is 10.30 m/s.

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