EASY
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The vector sum of two forces is perpendicular to their vector differences. In that case, the forces.

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Important Questions on Vector Algebra

HARD
Let v be a vector in the plane such that |v-i|=|v-2i|=|v-j|. Then |v| lies in the interval.
MEDIUM
The two vectors i^+j^+k^ and i^+3j^+5k^ represent the two sides AB and AC respectively of a ΔABC. The length of the median through A is
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The diagonals of a parallelogram are the vectors 3i^+6j^-2k^ and -i^-2j^-8k^ then, the length of the shorter side of parallelogram is
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If two forces of 3 units and 4 units are acting at an angle 90°, then its resultant forces will be

MEDIUM
 If a and b are unit vectors, then the greatest value of 3|a+b|+|a-b| is
 
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If a=2i^+5j^ and b=2i^-j^, then the unit vector along a+b will be
MEDIUM
If the sum of two unit vectors is again a unit vector, then magnitude of their difference is
HARD
In quadrilateral ABCD, AB=a, BC=b, DA=a-b, M is the midpoint of BC and X is a point on DM such that DX=45DM. Then the points A, X and C
HARD

In a triangle PQR , let a=QR, b=RP and c=PQ .

If a =3, b =4 and a.cbc.ab=aa+b, then the value of a×b2 is _______

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In a ABC, D, E, F are the mid-points of the sides BCCA and AB respectively, the vector AD is equal to
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The two adjacent sides of parallelogram are 2i^-4j^+5k^ and i^-2j^-3k^. The unit vector parallel to its diagonal which starts at the common vertex of the above two sides, is
MEDIUM
If 3i^+2j^-5k^=x2i^-j^+k^+yi^+3j^-2k^+z-2i^+j^-3k^, then
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If A=3i^-2j^+k^B=i^-3j^+5k^ and  C=2i^+j^-4k^ form a right angled triangle then out of the following which one is satisfied?
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If i^+4j^+3k^,i^+2j^+3k^,3i^+2j^+k^ are position vectors of A,B,C respectively and if D,E are mid points of sides BC and AC, then DE is equal to
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If a=2ı^+3ȷ^-4k^ and b=ı^+3ȷ^+2k^, then a unit vector in the direction of a+b is
HARD

Prove by vector method that: cos(A-B)=cosAcosB+sinAsinB.

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The resultant of two forces P and Q is R. If Q is doubled, then the new resultant will be perpendicular to P. Prove that Q=R.

MEDIUM
Let u and v be two vectors. Then, u-v=|u-v| if and only if
HARD
Let PR=3i^+j^-2k^&SQ=i^-3j^-4k^ determine diagonals of a parallelogram PQRS and PT=i^+2j^+3k^ be another vector. Then the volume (in cubic unit) of the parallelepiped determined by the vectors PT, PQ & PS  is
HARD
If the vectors AB=3i^+4k^ and AC=5i^-2j^+4k^ are the sides of a triangle ABC, then the length of the median through A is: