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Let Tbe triangular region with vertices (0,0),(1,1),and(1,-1)

If the density at each point in Tis proportional to the point’s distance from the x-axis, find the center of mass of T.

Short Answer

Expert verified

Mass is k3.

Moment of Mass are My=k4and Mx=k6.

Center of mass are x¯=34,y¯=12

Step by step solution

01

Given Information

Vertices of triangular region are (0,0),(1,1),and(1,-1)

Density is proportional to point's distance from xaxis.

ÒÏ(x,y)=ky

02

Mass of Triangular Region

Mass of triangle = Twice the mass of upper triangle.

m=2∫01∫0xkydydxm=∬ΩÒÏ(x,y)dA

m=2k∫01y220xdx

m=k∫01x2dx

m=kx3301

m=k3

03

First Moment of Mass about y axis

My=∬ΩxÒÏ(x,y)dA

Putting limits

My=∫01∫-xxxkydydx[ÒÏ(x,y)=ky]

Do half the limit and twice the integral as per the given figure.

My=2∫01∫0xxkydydx

My=2k∫01y220xxdx

My=k∫01x3dx

My=x4401k=k4

04

First Moment of Mass about x axis

Mx=∬ΩyÒÏ(x,y)dA

Putting limits

Mx=∫01∫-xxky2dydx[ÒÏ(x,y)=ky]

Solving inner integral first

Mx=k∫01y33-xxdx

Mx=k∫01(x)3-(-x)33dx

Mx=23k∫01x3dx

Mx=23kx4401=k6

05

Center of Mass

The coordinates are x¯=Mym,y¯=Mxm

x¯=kkk3,y¯=6kk3

x¯=34,y¯=12

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