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The value of veca.(vecb+vecc)xx(veca+vec...

The value of `veca.(vecb+vecc)xx(veca+vecb+vecc)`, is

A

`2[veca vecb vecc]`

B

`[veca vecb vecc]`

C

0

D

None of these

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem \( \vec{a} \cdot (\vec{b} + \vec{c}) \times (\vec{a} + \vec{b} + \vec{c}) \), we will follow these steps: ### Step 1: Expand the expression We start by expanding the expression using the distributive property of the dot product and the cross product. \[ \vec{a} \cdot (\vec{b} + \vec{c}) \times (\vec{a} + \vec{b} + \vec{c}) = \vec{a} \cdot \left( \vec{b} \times (\vec{a} + \vec{b} + \vec{c}) + \vec{c} \times (\vec{a} + \vec{b} + \vec{c}) \right) \] ### Step 2: Calculate the cross products Now, we will calculate the cross products separately. 1. **Calculate \( \vec{b} \times (\vec{a} + \vec{b} + \vec{c}) \)**: \[ \vec{b} \times (\vec{a} + \vec{b} + \vec{c}) = \vec{b} \times \vec{a} + \vec{b} \times \vec{b} + \vec{b} \times \vec{c} \] Since \( \vec{b} \times \vec{b} = \vec{0} \), we have: \[ \vec{b} \times (\vec{a} + \vec{b} + \vec{c}) = \vec{b} \times \vec{a} + \vec{b} \times \vec{c} \] 2. **Calculate \( \vec{c} \times (\vec{a} + \vec{b} + \vec{c}) \)**: \[ \vec{c} \times (\vec{a} + \vec{b} + \vec{c}) = \vec{c} \times \vec{a} + \vec{c} \times \vec{b} + \vec{c} \times \vec{c} \] Since \( \vec{c} \times \vec{c} = \vec{0} \), we have: \[ \vec{c} \times (\vec{a} + \vec{b} + \vec{c}) = \vec{c} \times \vec{a} + \vec{c} \times \vec{b} \] ### Step 3: Combine the results Now we can combine the results from the two cross products: \[ \vec{a} \cdot \left( \vec{b} \times \vec{a} + \vec{b} \times \vec{c} + \vec{c} \times \vec{a} + \vec{c} \times \vec{b} \right) \] ### Step 4: Evaluate the dot products Now we evaluate the dot products: 1. \( \vec{a} \cdot (\vec{b} \times \vec{a}) = 0 \) (since the dot product of a vector with itself is zero) 2. \( \vec{a} \cdot (\vec{c} \times \vec{c}) = 0 \) (same reason) 3. \( \vec{a} \cdot (\vec{b} \times \vec{c}) \) remains as it is. 4. \( \vec{a} \cdot (\vec{c} \times \vec{b}) = -\vec{a} \cdot (\vec{b} \times \vec{c}) \) (using the property of the scalar triple product) ### Step 5: Combine the results Thus, we have: \[ 0 + \vec{a} \cdot (\vec{b} \times \vec{c}) - \vec{a} \cdot (\vec{b} \times \vec{c}) = 0 \] ### Final Result The value of \( \vec{a} \cdot (\vec{b} + \vec{c}) \times (\vec{a} + \vec{b} + \vec{c}) \) is: \[ \boxed{0} \]

To solve the problem \( \vec{a} \cdot (\vec{b} + \vec{c}) \times (\vec{a} + \vec{b} + \vec{c}) \), we will follow these steps: ### Step 1: Expand the expression We start by expanding the expression using the distributive property of the dot product and the cross product. \[ \vec{a} \cdot (\vec{b} + \vec{c}) \times (\vec{a} + \vec{b} + \vec{c}) = \vec{a} \cdot \left( \vec{b} \times (\vec{a} + \vec{b} + \vec{c}) + \vec{c} \times (\vec{a} + \vec{b} + \vec{c}) \right) \] ...
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OBJECTIVE RD SHARMA ENGLISH-SCALAR AND VECTOR PRODUCTS OF THREE VECTORS -Exercise
  1. The value of veca.(vecb+vecc)xx(veca+vecb+vecc), is

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  2. For non-zero vectors veca, vecb and vecc , |(veca xx vecb) .vecc| = |v...

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  3. Let veca=hati+hatj-hatk, vecb=hati-hatj+hatk and vecc be a unit vector...

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  4. If veca lies in the plane of vectors vecb and vecc, then which of the ...

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  5. The value of [(veca-vecb, vecb-vecc, vecc-veca)], where |veca|=1, |vec...

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  6. If veca , vecb , vecc are three mutually perpendicular unit ve...

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  7. If vecr.veca=vecr.vecb=vecr.vecc=0 for some non-zero vectro vecr, then...

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  8. If the vectors ahati+hatj+hatk, hati+bhatj+hatk, hati+hatj+chatk(a!=1,...

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  9. If hata, hatb, hatc are three units vectors such that hatb and hatc ar...

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  10. For any three vectors veca, vecb, vecc the vector (vecbxxvecc)xxveca e...

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  11. for any three vectors, veca, vecb and vecc , (veca-vecb) . (vecb -vecc...

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  12. For any vectors vecr the value of hatixx(vecrxxhati)+hatjxx(vecrxxha...

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  13. If the vectors veca=hati+ahatj+a^(2)hatk, vecb=hati+bhatj+b^(2)hatk, v...

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  14. Let veca,vecb,vecc be three noncolanar vectors and vecp,vecq,vecr are ...

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  15. If vecA, vecB and vecC are three non - coplanar vectors, then (vecA.ve...

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  16. Let veca=a(1)hati+a(2)hatj+a(3)hatk,vecb=b(1)hati+b(2)hatj+b(3)hatk an...

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  17. If non-zero vectors veca and vecb are perpendicular to each ot...

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  18. show that (vecaxxvecb)xxvecc=vecaxx(vecbxxvecc) if and only if veca a...

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  19. If veca,vecb, vecc and vecp,vecq,vecr are reciprocal system of vectors...

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  20. vecaxx(vecaxx(vecaxxvecb)) equals

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  21. If veca =hati + hatj, vecb = hati - hatj + hatk and vecc is a unit vec...

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