A rod of length 30.0 cm has linear density (mass per length) given by l 5 50.0 1 20.0x where x is the distance from one end, measured in meters, and l is in grams/meter. (a) What is the mass of the rod? (b) How far from the x 5 0 end is its center of mass?

Respuesta :

Answer:

(a). The mass of the rod is 15.9 g.

(b). The center of mass is 0.153 m.

Explanation:

Given that,

Length = 30.0 cm

Linear density [tex]\labda=50.0+20.0x[/tex]

We need to calculate the mass of rod

Using formula of mass

[tex]M=\int{dm}[/tex]

[tex]M=\int{(50.0+20.0x)dx}[/tex]

[tex]M=50.0x+10x^2[/tex]

Put the value of x

[tex]M=50.0\times0.30+10\times(0.30)^2[/tex]

[tex]M=15.9\ g[/tex]

We need to calculate center of mass

The center of mass has an x coordinate is given by

[tex]x_{cm}=\dfrac{\int{xdm}}{\int{dm}}[/tex]

We need to calculate the value of  [tex]\int{xdm}[/tex]

[tex]\int{xdm}=\int{(50.0x+20.0x^2)dx}[/tex]

[tex]\int{xdm}=25x^2+\dfrac{20}{3}x^3[/tex]

Put the value into the formula

[tex]\int{xdm}=25\times0.3^2+\dfrac{20}{3}\times(0.3)^3[/tex]

[tex]\int{xdm}=2.43[/tex]

Put the value into the formula of center of mass

[tex]x_{cm}=\dfrac{2.43}{15.9}[/tex]

[tex]x_{cm}=0.153\ m[/tex]

Hence, (a). The mass of the rod is 15.9 g.

(b). The center of mass is 0.153 m.

A) The mass of the rod = 15.9 grams

B) The position of the center of mass = 0.153 m

Given data :

Length of rod ( x ) = 30 cm  = 0.30 m

Linear density = 50.0 + 20.0x

A) Determine the mass ( m ) of the rod by integrating the Linear density

M = ∫ dm.dx

   = ∫ ( 50.0 + 20.0x ) dx

∴ M = 50x + 20x² ----- ( 1 )

Input the value of x into equation ( 1 )

M = 50 ( 0.30 ) + 20 ( 0.30 )² = 15.9 grams

B) Determine the value of the position ( x ) of the center of mass

applying the formula below

x = ∫ [tex]\frac{xdm}{dm}[/tex]  ----- ( 2 )

first step : calculate the value of  ∫ xdm

∫ xdm  = ∫ ( 50x + 20x² ) dx

           = 25x² + [tex]\frac{20}{3} x^{3}[/tex]  -------- ( 3 )

where ; x = 0.30 m   ( input value into equation 3 )

∴ ∫ xdm = 2.43

Back to equation ( 2 )

X = 2.43 / 15.9

   = 0.153 m.

Hence we can conclude that ; The mass of the rod = 15.9 grams,  The position of the center of mass = 0.153 m

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