Common Core: High School - Number and Quantity : Magnitude and Direction of a Vector Sum: CCSS.Math.Content.HSN-VM.B.4b

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Example Questions

Example Question #1 : Magnitude And Direction Of A Vector Sum: Ccss.Math.Content.Hsn Vm.B.4b

If \(\displaystyle \left \| v\right \|=10\), and \(\displaystyle \left \| w\right \|=5\), and the angle in between them is \(\displaystyle 60^{\circ}\), find the magnitude of the resultant vector. 

Possible Answers:

\(\displaystyle \left \| v+w\right \|=15\)

\(\displaystyle \left \| v+w\right \|=\sqrt{65}\)

\(\displaystyle \left \| v+w\right \|=\sqrt{75}\)

\(\displaystyle \left \| v+w\right \|=7\)

\(\displaystyle \left \| v+w\right \|=\sqrt{85}\)

Correct answer:

\(\displaystyle \left \| v+w\right \|=\sqrt{75}\)

Explanation:

In order to find the resultants magnitude, we need to use the law of cosines. The law of cosines is \(\displaystyle c^2=a^2+b^2-2ab\cos(C)\). Suppose that \(\displaystyle a=10\)\(\displaystyle b=5\), and \(\displaystyle C=60^{\circ}\), then

\(\displaystyle c^2=10^2+5^2-2\cdot10\cdot5\cos(60^{\circ})\)

\(\displaystyle c^2=100+25-20\cdot5\cos(60^{\circ})\)

\(\displaystyle c^2=125-100\cos(60^{\circ})\)

\(\displaystyle c^2=125-100\cdot\frac{1}{2}\)

\(\displaystyle c^2=125-50\)

\(\displaystyle c^2=75\)

\(\displaystyle \sqrt{c^2}=\sqrt{75}\)

\(\displaystyle c=\sqrt{75}\approx8.66\)

 

Here is a visual representation of what we just found.

 

Locs

Example Question #2 : Magnitude And Direction Of A Vector Sum: Ccss.Math.Content.Hsn Vm.B.4b

If \(\displaystyle \left \| v\right \|=11\), and \(\displaystyle \left \| w\right \|=21\), and the angle in between them is \(\displaystyle 21^{\circ}\), find the magnitude of the resultant vector.

Possible Answers:

\(\displaystyle \left \| v+w\right \|=11.5\)

\(\displaystyle \left \| v+w\right \|=\sqrt{85}\)


\(\displaystyle \left \| v+w\right \|=12\)

\(\displaystyle \left \| v+w\right \|=11.6\)

\(\displaystyle \left \| v+w\right \|=11.43\)

 

Correct answer:

\(\displaystyle \left \| v+w\right \|=11.43\)

 

Explanation:

In order to find the resultants magnitude, we need to use the law of cosines. The law of cosines is \(\displaystyle c^2=a^2+b^2-2ab\cos(C)\). Suppose that \(\displaystyle a=11\)\(\displaystyle b=21\), and \(\displaystyle C=21^{\circ}\), then

\(\displaystyle c^2=11^2+21^2-2\cdot11\cdot21\cos(21^{\circ})\)

\(\displaystyle c^2=121+441-462\cos(21^{\circ})\)

\(\displaystyle c^2=562-462\cos(21^{\circ})\)

\(\displaystyle c^2=562-462\cdot0.9336\)

\(\displaystyle c^2=562-431.3142\)

\(\displaystyle c^2=130.6858\)

\(\displaystyle \sqrt{c^2}=\sqrt{130.6858}\)

\(\displaystyle c=\sqrt{130.6858}\approx11.43\)

 

Example Question #3 : Magnitude And Direction Of A Vector Sum: Ccss.Math.Content.Hsn Vm.B.4b

If \(\displaystyle \left \| v\right \|=8\), and \(\displaystyle \left \| w\right \|=22\), and the angle in between them is \(\displaystyle 103^{\circ}\), find the magnitude of the resultant vector. 

Possible Answers:

\(\displaystyle \left \| v+w\right \|=22.04\)

\(\displaystyle \left \| v+w\right \|=24.04\)

\(\displaystyle \left \| v+w\right \|=25.04\)

 

\(\displaystyle \left \| v+w\right \|=21.04\)

\(\displaystyle \left \| v+w\right \|=23.04\)

Correct answer:

\(\displaystyle \left \| v+w\right \|=25.04\)

 

Explanation:

In order to find the resultants magnitude, we need to use the law of cosines. The law of cosines is \(\displaystyle c^2=a^2+b^2-2ab\cos(C)\). Suppose that \(\displaystyle a=8\)\(\displaystyle b=22\), and \(\displaystyle C=103^{\circ}\), then

\(\displaystyle c^2=8^2+22^2-2\cdot8\cdot22\cos(103^{\circ})\)

\(\displaystyle c^2=64+484-16\cdot22\cos(103^{\circ})\)

\(\displaystyle c^2=548-352\cos(103^{\circ})\)

\(\displaystyle c^2=548-352\cdot-0.2249511\)

\(\displaystyle c^2=548+79.18277\)

\(\displaystyle c^2=627.1828\)

\(\displaystyle \sqrt{c^2}=\sqrt{627.1828}\)

\(\displaystyle c=\sqrt{627.1828}\approx25.04\)

Example Question #4 : Magnitude And Direction Of A Vector Sum: Ccss.Math.Content.Hsn Vm.B.4b

If \(\displaystyle \left \| v\right \|=1\), and \(\displaystyle \left \| w\right \|=38\), and the angle in between them is \(\displaystyle 116^{\circ}\), find the magnitude of the resultant vector.

Possible Answers:

\(\displaystyle \left \| v+w\right \|=40.8\)

\(\displaystyle \left \| v+w\right \|=41.34\)

\(\displaystyle \left \| v+w\right \|=38.6\)

\(\displaystyle \left \| v+w\right \|=38.5\)

\(\displaystyle \left \| v+w\right \|=38.45\)

 

Correct answer:

\(\displaystyle \left \| v+w\right \|=38.45\)

 

Explanation:

In order to find the resultants magnitude, we need to use the law of cosines. The law of cosines is \(\displaystyle c^2=a^2+b^2-2ab\cos(C)\). Suppose that \(\displaystyle a=1\)\(\displaystyle b=38\), and \(\displaystyle C=116^{\circ}\), then

\(\displaystyle c^2=1^2+38^2-2\cdot1\cdot38\cos(116^{\circ})\)

\(\displaystyle c^2=1+1444-2\cdot38\cos(116^{\circ})\)

\(\displaystyle c^2=1445-76\cos(116^{\circ})\)

\(\displaystyle c^2=1445-76\cdot-.4383711\)

\(\displaystyle c^2=1445+33.31621\)

\(\displaystyle c^2=1478.316\)

\(\displaystyle \sqrt{c^2}=\sqrt{1478.316}\)

\(\displaystyle c=\sqrt{1478.316}\approx38.45\)

 

Example Question #5 : Magnitude And Direction Of A Vector Sum: Ccss.Math.Content.Hsn Vm.B.4b

If \(\displaystyle \left \| v\right \|=18\), and \(\displaystyle \left \| w\right \|=16\), and the angle in between them is \(\displaystyle 26^{\circ}\), find the magnitude of the resultant vector. 

Possible Answers:

\(\displaystyle \left \| v+w\right \|=9.62\)

\(\displaystyle \left \| v+w\right \|=11.43\)

\(\displaystyle \left \| v+w\right \|=4.67\)

\(\displaystyle \left \| v+w\right \|=7.89\)

 

\(\displaystyle \left \| v+w\right \|=20.27\)

Correct answer:

\(\displaystyle \left \| v+w\right \|=7.89\)

 

Explanation:

In order to find the resultants magnitude, we need to use the law of cosines. The law of cosines is \(\displaystyle c^2=a^2+b^2-2ab\cos(C)\). Suppose that \(\displaystyle a=10\)\(\displaystyle b=5\), and \(\displaystyle C=60^{\circ}\), then

\(\displaystyle c^2=18^2+16^2-2\cdot18\cdot16\cos(26^{\circ})\)

\(\displaystyle c^2=324+256-36\cdot16\cos(26^{\circ})\)

\(\displaystyle c^2=580-576\cos(26^{\circ})\)

\(\displaystyle c^2=580-517.7054\)

\(\displaystyle c^2=62.2946\)

\(\displaystyle \sqrt{c^2}=\sqrt{62.2946}\)

\(\displaystyle c=\sqrt{62.2946}\approx7.89\)

Example Question #6 : Magnitude And Direction Of A Vector Sum: Ccss.Math.Content.Hsn Vm.B.4b

If \(\displaystyle \left \| v\right \|=16\), and \(\displaystyle \left \| w\right \|=19\), and the angle in between them is \(\displaystyle 150^{\circ}\), find the magnitude of the resultant vector. 

Possible Answers:

\(\displaystyle \left \| v+w\right \|=33.82\)

 

\(\displaystyle \left \| v+w\right \|=40.58\)

\(\displaystyle \left \| v+w\right \|=31.42\)

\(\displaystyle \left \| v+w\right \|=30.8\)

\(\displaystyle \left \| v+w\right \|=36.87\)

Correct answer:

\(\displaystyle \left \| v+w\right \|=33.82\)

 

Explanation:

In order to find the resultants magnitude, we need to use the law of cosines. The law of cosines is \(\displaystyle c^2=a^2+b^2-2ab\cos(C)\). Suppose that \(\displaystyle a=16\)\(\displaystyle b=19\), and \(\displaystyle C=150^{\circ}\), then

\(\displaystyle c^2=16^2+19^2-2\cdot16\cdot19\cos(150^{\circ})\)

\(\displaystyle c^2=256+361-32\cdot19\cos(150^{\circ})\)

\(\displaystyle c^2=617-608\cos(150^{\circ})\)

\(\displaystyle c^2=617-608\cdot-0.8660254\)

\(\displaystyle c^2=1143.543\)

\(\displaystyle \sqrt{c^2}=\sqrt{1143.543}\)

\(\displaystyle c=\sqrt{1143.543}\approx33.82\)

Example Question #7 : Magnitude And Direction Of A Vector Sum: Ccss.Math.Content.Hsn Vm.B.4b

If \(\displaystyle \left \| v\right \|=34\), and \(\displaystyle \left \| w\right \|=17\), and the angle in between them is \(\displaystyle 10^{\circ}\), find the magnitude of the resultant vector. 

Possible Answers:

\(\displaystyle \left \| v+w\right \|=13.56\)

\(\displaystyle \left \| v+w\right \|=17.84\)

\(\displaystyle \left \| v+w\right \|=18.09\)

\(\displaystyle \left \| v+w\right \|=14.69\)

\(\displaystyle \left \| v+w\right \|=17.51\)

Correct answer:

\(\displaystyle \left \| v+w\right \|=17.51\)

Explanation:

In order to find the resultants magnitude, we need to use the law of cosines. The law of cosines is \(\displaystyle c^2=a^2+b^2-2ab\cos(C)\). Suppose that \(\displaystyle a=17\)\(\displaystyle b=10\), and \(\displaystyle C=10^{\circ}\), then

\(\displaystyle c^2=17^2+34^2-2\cdot34\cdot17\cos(10^{\circ})\)

\(\displaystyle c^2=289+1156-34\cdot34\cos(10^{\circ})\)

\(\displaystyle c^2=1445-1156\cos(10^{\circ})\)

\(\displaystyle c^2=1445-1138.438\)

\(\displaystyle c^2=306.562\)

\(\displaystyle \sqrt{c^2}=\sqrt{306.562}\)

\(\displaystyle c=\sqrt{306.562}\approx17.51\)

Example Question #8 : Magnitude And Direction Of A Vector Sum: Ccss.Math.Content.Hsn Vm.B.4b

If \(\displaystyle \left \| v\right \|=18\), and \(\displaystyle \left \| w\right \|=19\), and the angle in between them is \(\displaystyle 131^{\circ}\), find the magnitude of the resultant vector. 

Possible Answers:

\(\displaystyle \left \| v+w\right \|=37.92\)

\(\displaystyle \left \| v+w\right \|=31.56\)

\(\displaystyle \left \| v+w\right \|=34.90\)

\(\displaystyle \left \| v+w\right \|=33.67\)

 

\(\displaystyle \left \| v+w\right \|=32.89\)

Correct answer:

\(\displaystyle \left \| v+w\right \|=33.67\)

 

Explanation:

In order to find the resultants magnitude, we need to use the law of cosines. The law of cosines is \(\displaystyle c^2=a^2+b^2-2ab\cos(C)\). Suppose that \(\displaystyle a=18\)\(\displaystyle b=2\), and \(\displaystyle C=106^{\circ}\), then

\(\displaystyle c^2=18^2+19^2-2\cdot18\cdot19\cos(131^{\circ})\)

\(\displaystyle c^2=324+361-36\cdot19\cos(131^{\circ})\)

\(\displaystyle c^2=685-684\cos(131^{\circ})\)

\(\displaystyle c^2=685-684\cdot-0.656059\)

\(\displaystyle c^2=685+448.7444\)

\(\displaystyle c^2=1133.744\)

\(\displaystyle \sqrt{c^2}=\sqrt{1133.744}\)

\(\displaystyle c=\sqrt{1133.744}\approx33.67\)

Example Question #1 : Magnitude And Direction Of A Vector Sum: Ccss.Math.Content.Hsn Vm.B.4b

If \(\displaystyle \left \| v\right \|=4\), and \(\displaystyle \left \| w\right \|=23\), and the angle in between them is \(\displaystyle 149^{\circ}\), find the magnitude of the resultant vector. 

Possible Answers:

\(\displaystyle \left \| v+w\right \|=27.23\)

 

\(\displaystyle \left \| v+w\right \|=26.42\)

\(\displaystyle \left \| v+w\right \|=27.76\)

\(\displaystyle \left \| v+w\right \|=28.13\)

\(\displaystyle \left \| v+w\right \|=24.57\)

Correct answer:

\(\displaystyle \left \| v+w\right \|=27.23\)

 

Explanation:

In order to find the resultants magnitude, we need to use the law of cosines. The law of cosines is \(\displaystyle c^2=a^2+b^2-2ab\cos(C)\). Suppose that \(\displaystyle a=4\)\(\displaystyle b=23\), and \(\displaystyle C=149^{\circ}\), then

\(\displaystyle c^2=4^2+23^2-2\cdot4\cdot23\cos(149^{\circ})\)

\(\displaystyle c^2=16+529-8\cdot23\cos(149^{\circ})\)

\(\displaystyle c^2=545-184\cos(149^{\circ})\)

\(\displaystyle c^2=545-184\cdot-0.8571673\)

\(\displaystyle c^2=584+157.7188\)

\(\displaystyle c^2=741.7188\)

\(\displaystyle \sqrt{c^2}=\sqrt{741.7188}\)

\(\displaystyle c=\sqrt{741.7188}\approx27.23\)

 

Example Question #2 : Magnitude And Direction Of A Vector Sum: Ccss.Math.Content.Hsn Vm.B.4b

If \(\displaystyle \left \| v\right \|=14\), and \(\displaystyle \left \| w\right \|=1\), and the angle in between them is \(\displaystyle 76^{\circ}\), find the magnitude of the resultant vector. 

Possible Answers:

\(\displaystyle \left \| v+w\right \|=14.09\)

\(\displaystyle \left \| v+w\right \|=13.79\)

 

\(\displaystyle \left \| v+w\right \|=17.94\)

\(\displaystyle \left \| v+w\right \|=13.62\)

\(\displaystyle \left \| v+w\right \|=14.25\)

Correct answer:

\(\displaystyle \left \| v+w\right \|=13.79\)

 

Explanation:

In order to find the resultants magnitude, we need to use the law of cosines. The law of cosines is \(\displaystyle c^2=a^2+b^2-2ab\cos(C)\). Suppose that \(\displaystyle a=14\)\(\displaystyle b=1\), and \(\displaystyle C=76^{\circ}\), then

\(\displaystyle c^2=14^2+1^2-2\cdot14\cdot1\cos(76^{\circ})\)

\(\displaystyle c^2=196+1-28\cdot1\cos(76^{\circ})\)

\(\displaystyle c^2=197-28\cos(76^{\circ})\)

\(\displaystyle c^2=197-28\cdot0.2419219\)

\(\displaystyle c^2=197-6.773813\)

\(\displaystyle c^2=190.2262\)

\(\displaystyle \sqrt{c^2}=\sqrt{190.2262}\)

\(\displaystyle c=\sqrt{190.2262}\approx13.79\)

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