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The masses and coordinates of four particles are as follows: 35 g, x = 2.0 cm, y

ID: 1450540 • Letter: T

Question

The masses and coordinates of four particles are as follows: 35 g, x = 2.0 cm, y = 2.0 cm; 45 g, x = 0.0 cm, y = 4.0 cm; 25 g, x = -3.0 cm, y = -3.0 cm, 40 g, x = -3.0 cm, y = 4.0 cm.

What is the rotational inertia of this collection with aspect to the x-axis ( kg m2)? 7.25E-5kg*m^2 Incorrect.

What is the rotational inertia of this collection with aspect to the y-axis? 1.725*10^4kg*m^2 Incorrect.

What is the rotational inertia of this collection with aspect to the z-axis? 5.85E-3 kg*m^2 Incorrect.

Explanation / Answer

m1 = 35 g = 0.035 kg .      ( x1 , y1 ) = (2 , 2) cm

m2 = 45 g = 0.045 kg            ( x2 , y2 ) = ( 0 , 4 ) cm

m3 = 25 g = 0.025 kg           ( x3 , y3 )   = (-3 , -3 ) cm

m4 = 40 g = 0.040 kg              (x4 , y4 )     = (-3 , 4 )   cm

Moment of inertia about X axis .

   IX    = 10-7 *( 35*22   + 45*42 + 25*32 + 40*42 ) = 1.725*10-4   kg*m2

Moment of inertia about Y axis

   IY = 10-7 *( 35*22   + 45*02 + 25*32 + 40*32 ) = 0.725*10-4   kg*m2

Moment of inertia about Z axis

     IZ   = 10-7 *{ 35*(22 + 22) + 45*(02 + 42) + 25*(32 + 32) + 40*(32 + 42 ) = 2.45*10-4   kg*m2