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Q22PE

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College Physics (Urone)
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Short Answer

A farmer wants to fence off his four-sided plot of flat land. He measures the first three sides, shown asA ,B , andC in Figure 3.62, and then correctly calculates the length and orientation of the fourth side D. What is his result?

The length of the fourth side Dis role="math" localid="1668685823714" 2.97 kmand oriented to 22.16°the west of south.

See the step by step solution

Step by Step Solution

Step 1: Resultant vector

When two or more vectors with various magnitudes and directions are put together following the triangle law of vector addition, the resultant vector has the same impact as one vector.

Step 2: Given data

  • The magnitude of the vectorA is, A=4.70 km.
  • The direction of the vectorA is 7.5°south of east.
  • The magnitude of the vectorB is,B=2.48 km .
  • The direction of the vectorB is 16°west of north.
  • The magnitude of the vectorC is, C=3.02 km.
  • The direction of the vector Cis 19°north of west.

Step 3: Horizontal component of the resultant vector

The horizontal component of the vectorA is,

Ax=Acos7.5°

Here Ais the magnitude of the vector A.

Substitute 4.70 kmfor Ain the above expression, we get,

Ax=4.70 km×cos7.5°=4.66 km

The horizontal component of the vectorB is,

Bx=-Bsin16°

Here Bis the magnitude of the vectorB .

Substitute 2.48 kmfor B in the above expression, we get,

Bx=-2.48 km×sin16°=-0.68 km

The horizontal component of the vector C is,

Cx=-Ccos19°

Here Cis the magnitude of the vectorC .

Substitute 3.02 kmfor Cin the above expression, we get,

Cx=-3.02 km×cos19°=-2.86 km

The horizontal component of the resultant vectorD is,

Dx=Ax+Bx+Cx

Substitute 4.66 kmforAx , -0.68 kmfor Bx, and-2.86 km forCx in the above expression, we get,

Dx=4.66 km+-0.68 km+-2.86 km=1.12 km

Step 4: Vertical component of the resultant vector A, B

The vertical component of the vector Ais,

Ay=-Asin7.5°

HereA is the magnitude of the vector A.

Substitute 4.70 kmfor Ain the above expression, we get,

Ay=-4.70 km×sin7.5°=-0.61 km

The vertical component of the vectorB is,

By=Bcos16°

Here Bis the magnitude of the vectorB .

Substitute 2.48 kmfor B in the above expression, we get,

By=2.48 km×cos16°=2.38 km

Step 5: Vertical component of the resultant vector C, D

The vertical component of the vectorC is,

Cy=Csin19°

Here Cis the magnitude of the vectorC .

Substitute3.02 km for Cin the above expression, we get,

Cy=3.02 km×sin19°=0.98 km

The vertical component of the resultant vector Dis,

Dy=Ay+By+Cy

Substitute -0.61 kmforAy , 2.38 kmfor By, and0.98 km for Cyin the above expression, we get,

Dy=-0.61 km+2.38 km+0.98 km=2.75 km

Step 6: Magnitude and direction of the resultant vector

The magnitude of the resultant vector Dis,

D=Dx2+Dy2

Substitute1.12 km for Dx, and 2.75 kmfor Dy in the above expression, we get,

D=1.12 km2+2.75 km2=2.97 km

The direction of the resultant vectorD is,

θ=tan-1DxDy

Substitute for 1.12 km, Dxand for in the above expression, we get,

role="math" localid="1668687995126" θ=tan-11.122.75

θ=2216°

Hence, the length of the fourth sideD is2.97 km and oriented to 22.16°the west of south.

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