JEE ADVANCED - VOL - I VECTOR ALGEBRA
3 6................. iii
MULTI ANSWER QUESTIONS
on solving the equations (i), (ii) & (iii) , we have
49. As forces are in equilibrium we have 1, 2, 3
F1 F2 F3 F4 0 aˆ ^ ^ bˆ ^ ^
53. . a b . a b
^ ^ ^ a b
equating the coefficients of i , j , k and solve the
equations a b
50. Let point A be taken as origin. Then the position
or a b
. a b 0
vectors of B,C and D are a, a b and b a
respectively which is possible when a b
aba b a b
P.V.of M a
2 2
If angle between a and b is , then
DN : NM 4 :1
b a.a a a cos
4 a b a
P.V. of N 2 3 cos 1 , 00
5
ab
5
3 54. cos 2 sin 2 sin 2 1
AN AC
1
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5
3sin 2 1 sin 2
51. Given that 3
3 4q 3r 2q 3r
sin
1
3
10q 12r
6 tan 2
q r....... i
5 2) a.b c 0 , b c
a
0 , c
ab 0
5
(i) p =4 q + 3 q by u sin g (i ) a.b b.c c.a 0
6 2 2 2
3 a b a b 2a.b
p q
2 9 16 2 a b sin
p q and directions of p and q are same 2
a b 25 2 3 4 sin
6
(ii) p 4 r 3r = 25 24sin
5
9 a b 25 24sin
p r
5
52. We have, a b 25 24 7
i 3k 2i j r i j k a b 25 24 1
2i 5 j 6k range of a b is 1,7 25 24 1
On comparing, we get
2 2............ i 3) similarly we have calculate range of b c
5 .................(ii)
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57. According to the given conditions a.b 0 and
55. Let c c1iˆ c2 ˆj c3kˆ
2 b.c 0 , where c 0,1,0 . Thus
c12 c22 c32 iˆ ˆj 2
2x 2 3x 1 0 for x 0 . But
Also,
2x 2 3x 1 is greater than zero for all x 0
58. Let b xi yj . Since a is perpendicular to b so
c iˆ c ˆj c kˆ .iˆ ˆj c iˆ c ˆj c kˆ 1
1 2 3 1 2 3
4
2 2 2 4x 3y 0 . Thus b x i j . Let
3
c1 c2 c2 c3 1 c1 c3 and
c ui vj be the required vector. According
c2 1 c3 to the given condition
2 1 c.a
Hence from (1), 3c3 2c3 1 0 c3 1 4u 3v 5 .
3 a
1
or 1 when c3 c.b ux vx
3 2 2
Also b x 2 1
c iˆ 4 ˆj kˆ when c3 1, c iˆ kˆ
1
3
3u 4v 10
Solving these equations we have
D C
u 2 and v 1 or u ,v 11/ 5
59. The diagonals are given by
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6, 1
E AB BC 4i 2j 4k, AB BC 2i 2j
56. These vectors have magnitudes 6 and 2 2 ,
respectively, and their dot product is 12.
B
A 1, 2 Therefore the angle between them is
E is the mid-point of A and C 12 1 3
cos1 cos1 or
Position vector of C is 11i 6 2 2 2 4 4
AEB DEA 60.
2 ADE is right angled at E
AB 2 AD 2 2 AE 2 h Area ABC
1
If B or D is x, y 3
2 2 1
BE. AE 0 h AB AC
3 2
and DE. AE 0
5 x y 29 D
2 2
and x 1 y 2 52
4 h
x 2 12 x 35 0
A1,1,1
x 5, y 4
2
x 7, y 6 E
B D1 C
OB 7i 6 j OD 5i 4 j and area = 1, 0, 0 2, 0, 0 3, 0, 0
52 sq.units
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