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Vectors Practice Questions - DPP for NEET

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1. (d)
90
2 sin
2
vv
° æö
D=
ç÷
èø
1
2sin4522
2
v vv = °= ´=
22
2 21
60 30
pp
=´w=´´ = r cm/s
2. (b) 2 sin
2
vv
q æö
D=
ç÷
èø
10
2 5 sin 45
2
= ´ ´ °=
\ 
v
a
t
D
=
D
 
10/21
10 2
==
 m/s
2
3. (c) For motion of the particle from (0, 0) to (a, 0)
$
ˆˆ
(0) FKi aj FKaj =- + Þ =-
ur ur
Displacement 
ˆˆ ˆˆ
( 0) (0 0) r ai j i j ai = + - +=
r
$
So work done from (0, 0) to (a, 0) is given by
$
. .0 W F r Ka j ai = =-=
urr
$
For motion (a, 0) to (a, a)
$
() F K ai aj =-+
ur
$
 and displacement
 
$
ˆ ˆ ˆˆ
( ) ( 0) r ai aj ai j a j = + - +=
r
So work done from (a, 0) to (a, a)
$ $
2
. ( ).
urr
$
W F r K ai a j a j Ka = =- + =-
So total work done = 
2
Ka -
4. (d)
q
W
P
T
sin T q
cos T q
As the metal sphere is in equilibrium under the effect
of the three forces therefore
0 T PW + +=
ururuur
From the figure
cos TW q=
................... (i)
sin TP q=
................... (ii)
From equation (i) and (ii) we get
tan PW =q and 
2 22
T PW =+
5. (b) Time taken to cross the river along shortest possible
path is given by
22
=
-
d
t
vu
v = velocity of boat in still water
u = velocity of river water
d = width of river
22
151
60
5
\=
-u
Þ u = 3 km/h
6. (d) Here d = 320 m = 
320
km
1000
t = 4 min
v = 
5
3
u
Putting values in 
22
=
-
d
t
vu
, u = 60 m/min
7. (c)
12
sin sin sin150
P QR
==
q q°
Þ
 
1
1.93
sin sin150
R
=
q°
Þ
 
1
1.93 sin150 1.93 0.5
1
sin 0.9659
R
´ °´
= ==
q
P Q
R
150°
2
q
1
q
8. (b)
T
T cos 30°
T sin 30° 30 N
W
30°
Page 2


1. (d)
90
2 sin
2
vv
° æö
D=
ç÷
èø
1
2sin4522
2
v vv = °= ´=
22
2 21
60 30
pp
=´w=´´ = r cm/s
2. (b) 2 sin
2
vv
q æö
D=
ç÷
èø
10
2 5 sin 45
2
= ´ ´ °=
\ 
v
a
t
D
=
D
 
10/21
10 2
==
 m/s
2
3. (c) For motion of the particle from (0, 0) to (a, 0)
$
ˆˆ
(0) FKi aj FKaj =- + Þ =-
ur ur
Displacement 
ˆˆ ˆˆ
( 0) (0 0) r ai j i j ai = + - +=
r
$
So work done from (0, 0) to (a, 0) is given by
$
. .0 W F r Ka j ai = =-=
urr
$
For motion (a, 0) to (a, a)
$
() F K ai aj =-+
ur
$
 and displacement
 
$
ˆ ˆ ˆˆ
( ) ( 0) r ai aj ai j a j = + - +=
r
So work done from (a, 0) to (a, a)
$ $
2
. ( ).
urr
$
W F r K ai a j a j Ka = =- + =-
So total work done = 
2
Ka -
4. (d)
q
W
P
T
sin T q
cos T q
As the metal sphere is in equilibrium under the effect
of the three forces therefore
0 T PW + +=
ururuur
From the figure
cos TW q=
................... (i)
sin TP q=
................... (ii)
From equation (i) and (ii) we get
tan PW =q and 
2 22
T PW =+
5. (b) Time taken to cross the river along shortest possible
path is given by
22
=
-
d
t
vu
v = velocity of boat in still water
u = velocity of river water
d = width of river
22
151
60
5
\=
-u
Þ u = 3 km/h
6. (d) Here d = 320 m = 
320
km
1000
t = 4 min
v = 
5
3
u
Putting values in 
22
=
-
d
t
vu
, u = 60 m/min
7. (c)
12
sin sin sin150
P QR
==
q q°
Þ
 
1
1.93
sin sin150
R
=
q°
Þ
 
1
1.93 sin150 1.93 0.5
1
sin 0.9659
R
´ °´
= ==
q
P Q
R
150°
2
q
1
q
8. (b)
T
T cos 30°
T sin 30° 30 N
W
30°
12
DPP/ P 05
From the figure
T sin 30° = 30 ...(i)
T cos 30° = W ...(ii)
By solving equation (i) and (ii) we get
303 WN = and T = 60 N
9. (c) Relative velocity = 
ˆˆ ˆˆ ˆ ˆ
(3 4) (34) 68 i j i j ij + -- - =+
10. (c)
30°
90°
m
v
r
v
sin 30° = 
1
2
r
m
v
v
=
Þ
 
0.5
0.25
22
m
r
v
v= == m/s
11. (a) To cross the river in minimum time, the shift is given
by 
du
v
.
12. (d) Relative velocity = 10 + 5 = 15 m/s.
Time taken by the bird to cross the train =
120
8
15
= sec
13. (d)
vr = w´
r urr
$ $
$ $
3 4 1 18 13 2
5 66
i jk
i jk = - =- -+
-
$
$
14. (d) | | 3( .)
ur u r ur ur
A B AB ´=
sin 3 cos AB AB q=q
Þtan3 q=
Þ 60 q=°
Now |||| R AB =+
ur ur ur
22
2 cos A B AB = ++q
22
1
2
2
A B AB
æö
= ++
ç÷
èø
= 
2 2 1/2
() A B AB ++
15. (a)
$ $ $ $
(7 3 )( 3 5) r F i j k i jk t= ´ = + + - ++
r r ur
$$
$ $
$ $
7 3 1 14 38 16
3 15
i jk
i jk t= = -+
-
$
r
$
16. (b)| |.
ur ur ur ur
B AB A´=
Þ sin cos AB AB q=q
Þ tan1 q=
\
45 q=°
17. (a) .0 PQ =
u r ur
Þ 
2
2 30 aa - -=
Þ a = 3
18. (a)
21
u u r ur r
S rr =-
. W FS =
ur ur
= 
$ $ $ $
(4 3).(11 11 15) i j k i jk + + ++
$$
= (4 × 11 + 1 × 11 + 3 × 15) = 100 J
19. (c)
ˆˆ ˆ ˆ ˆˆ
3 2 , 35 A i j kB i jk = - + = -+
u r ur
, 
ˆ ˆˆ
24 C i jk = +-
ur
2 22
3 ( 2) 1 9 4 1 14 A = + - + = + +=
r
2 22
1 ( 3) 5 1 9 25 35 B= +- += + +=
r
222
2 1 ( 4) 4 1 16 21
r
C= + +- = ++=
As 
22
B AC =+ therefore ABC will be right angled
triangle.
20. (b)
12
12
.
cos
FF
FF
q=
rr
= 
ˆˆ ˆ ˆ ˆˆ
(5 10 20 ).(10 5 15 )
25 100 400. 100 25 225
i j k i jk + - --
+ + ++
50 50 300
525. 350
-+
=
Þ
 
1
cos
2
q=
45 \q=°
21. (a)
ˆˆ ˆˆ ˆ ˆ ˆˆ
4 32 r abc i j i jk i jk = + + = -- + - = +-
r
rrr
222
ˆ ˆˆ
ˆ
||
1 1 ( 1)
r i jk
r
r
r
+-
==
+ +-
 
ˆ ˆˆ
3
i jk +-
=
22. (a)
D C
A B
300 m
400 m
Displacement 
AC AB BC =+
uuu r uuu r u uu r
Page 3


1. (d)
90
2 sin
2
vv
° æö
D=
ç÷
èø
1
2sin4522
2
v vv = °= ´=
22
2 21
60 30
pp
=´w=´´ = r cm/s
2. (b) 2 sin
2
vv
q æö
D=
ç÷
èø
10
2 5 sin 45
2
= ´ ´ °=
\ 
v
a
t
D
=
D
 
10/21
10 2
==
 m/s
2
3. (c) For motion of the particle from (0, 0) to (a, 0)
$
ˆˆ
(0) FKi aj FKaj =- + Þ =-
ur ur
Displacement 
ˆˆ ˆˆ
( 0) (0 0) r ai j i j ai = + - +=
r
$
So work done from (0, 0) to (a, 0) is given by
$
. .0 W F r Ka j ai = =-=
urr
$
For motion (a, 0) to (a, a)
$
() F K ai aj =-+
ur
$
 and displacement
 
$
ˆ ˆ ˆˆ
( ) ( 0) r ai aj ai j a j = + - +=
r
So work done from (a, 0) to (a, a)
$ $
2
. ( ).
urr
$
W F r K ai a j a j Ka = =- + =-
So total work done = 
2
Ka -
4. (d)
q
W
P
T
sin T q
cos T q
As the metal sphere is in equilibrium under the effect
of the three forces therefore
0 T PW + +=
ururuur
From the figure
cos TW q=
................... (i)
sin TP q=
................... (ii)
From equation (i) and (ii) we get
tan PW =q and 
2 22
T PW =+
5. (b) Time taken to cross the river along shortest possible
path is given by
22
=
-
d
t
vu
v = velocity of boat in still water
u = velocity of river water
d = width of river
22
151
60
5
\=
-u
Þ u = 3 km/h
6. (d) Here d = 320 m = 
320
km
1000
t = 4 min
v = 
5
3
u
Putting values in 
22
=
-
d
t
vu
, u = 60 m/min
7. (c)
12
sin sin sin150
P QR
==
q q°
Þ
 
1
1.93
sin sin150
R
=
q°
Þ
 
1
1.93 sin150 1.93 0.5
1
sin 0.9659
R
´ °´
= ==
q
P Q
R
150°
2
q
1
q
8. (b)
T
T cos 30°
T sin 30° 30 N
W
30°
12
DPP/ P 05
From the figure
T sin 30° = 30 ...(i)
T cos 30° = W ...(ii)
By solving equation (i) and (ii) we get
303 WN = and T = 60 N
9. (c) Relative velocity = 
ˆˆ ˆˆ ˆ ˆ
(3 4) (34) 68 i j i j ij + -- - =+
10. (c)
30°
90°
m
v
r
v
sin 30° = 
1
2
r
m
v
v
=
Þ
 
0.5
0.25
22
m
r
v
v= == m/s
11. (a) To cross the river in minimum time, the shift is given
by 
du
v
.
12. (d) Relative velocity = 10 + 5 = 15 m/s.
Time taken by the bird to cross the train =
120
8
15
= sec
13. (d)
vr = w´
r urr
$ $
$ $
3 4 1 18 13 2
5 66
i jk
i jk = - =- -+
-
$
$
14. (d) | | 3( .)
ur u r ur ur
A B AB ´=
sin 3 cos AB AB q=q
Þtan3 q=
Þ 60 q=°
Now |||| R AB =+
ur ur ur
22
2 cos A B AB = ++q
22
1
2
2
A B AB
æö
= ++
ç÷
èø
= 
2 2 1/2
() A B AB ++
15. (a)
$ $ $ $
(7 3 )( 3 5) r F i j k i jk t= ´ = + + - ++
r r ur
$$
$ $
$ $
7 3 1 14 38 16
3 15
i jk
i jk t= = -+
-
$
r
$
16. (b)| |.
ur ur ur ur
B AB A´=
Þ sin cos AB AB q=q
Þ tan1 q=
\
45 q=°
17. (a) .0 PQ =
u r ur
Þ 
2
2 30 aa - -=
Þ a = 3
18. (a)
21
u u r ur r
S rr =-
. W FS =
ur ur
= 
$ $ $ $
(4 3).(11 11 15) i j k i jk + + ++
$$
= (4 × 11 + 1 × 11 + 3 × 15) = 100 J
19. (c)
ˆˆ ˆ ˆ ˆˆ
3 2 , 35 A i j kB i jk = - + = -+
u r ur
, 
ˆ ˆˆ
24 C i jk = +-
ur
2 22
3 ( 2) 1 9 4 1 14 A = + - + = + +=
r
2 22
1 ( 3) 5 1 9 25 35 B= +- += + +=
r
222
2 1 ( 4) 4 1 16 21
r
C= + +- = ++=
As 
22
B AC =+ therefore ABC will be right angled
triangle.
20. (b)
12
12
.
cos
FF
FF
q=
rr
= 
ˆˆ ˆ ˆ ˆˆ
(5 10 20 ).(10 5 15 )
25 100 400. 100 25 225
i j k i jk + - --
+ + ++
50 50 300
525. 350
-+
=
Þ
 
1
cos
2
q=
45 \q=°
21. (a)
ˆˆ ˆˆ ˆ ˆ ˆˆ
4 32 r abc i j i jk i jk = + + = -- + - = +-
r
rrr
222
ˆ ˆˆ
ˆ
||
1 1 ( 1)
r i jk
r
r
r
+-
==
+ +-
 
ˆ ˆˆ
3
i jk +-
=
22. (a)
D C
A B
300 m
400 m
Displacement 
AC AB BC =+
uuu r uuu r u uu r
DPP/ P 05
13
AC = 
2 2 22
(AB) (BC) (400) (300) 500m + = +=
Distance = AB+BC =400+300=700 m
23. (a)
ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆˆ
A 3i 2j k,B i 3j 5k,C 2i j 4k = - + = - + = -+
rr r
2 22
A 3 ( 2) 1 9 4 1 14 = + - + = + +=
r
2 22
B 1 ( 3) 5 1 9 25 35 = +-+= + + =
r
222
C 2 1 ( 4) 4 1 16 21 = + +- = ++=
uv
As 
22
B AC =+ therefore ABC will be right angled
triangle.
24. (a)AB0sin 00 ´ = \ q= \q= °
r r
Two vectors will be parallel to each other.
25. (a), 26 (b), 27. (b)
ˆ ˆˆ
2 11
1 11
r r
i jk
AB ´=
 = 
ˆ ˆˆ
( 1 1) (2 1) (2 1) i jk -- -+ -
= 
ˆ ˆ
jk -+
Unit vector perpendicular to A
r
 and B
r
 is 
ˆ ˆ
2
jk
æö
-+
ç÷
èø
.
Any vector whose magnitude is k (constant) times
ˆ ˆˆ
(2) i jk ++ is parallel to A
r
 so, unit vector 
ˆ ˆˆ
2
6
i jk ++
is parallel to A
r
.
28. (b) A B AB + =-
rr rr
Þ
A
2
 + B
2
 + 2AB cosq = A
2
 + B
2
 + 2AB cosq
Hence cos q = 0 which gives q = 90°
Also vector addition is commutative.
Hence A B BA +=+
rr rr
29. (a) Let P
r
 and 
Q
r
 are two vectors in opposite direction,
then their sum () P Q PQ +- =-
rr rr
If PQ =
r r
 then sum equal to zero.
30. (d) The resultant of two vectors of unequal magnitude
given by 
22
2 cos R A B AB = ++q cannot be zero
for any value of q.
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FAQs on Vectors Practice Questions - DPP for NEET

1. What are vectors in physics?
Ans. In physics, vectors are mathematical quantities that have both magnitude and direction. They are used to represent physical quantities such as displacement, velocity, and force.
2. How are vectors represented?
Ans. Vectors are represented using arrows. The length of the arrow represents the magnitude of the vector, and the direction of the arrow represents the direction of the vector.
3. What is the difference between scalars and vectors?
Ans. Scalars are physical quantities that have only magnitude, such as time, temperature, and mass. Vectors, on the other hand, have both magnitude and direction. For example, speed is a scalar quantity, while velocity (speed with direction) is a vector quantity.
4. What is the importance of vectors in physics?
Ans. Vectors are essential in physics as they allow us to accurately describe and analyze physical phenomena. They provide a mathematical framework to understand the motion, forces, and other quantities in the physical world.
5. How are vectors added or subtracted?
Ans. Vectors can be added or subtracted using the head-to-tail method. To add two vectors, place the tail of the second vector at the head of the first vector, and the resultant vector is drawn from the tail of the first vector to the head of the second vector. To subtract vectors, add the negative of the vector to be subtracted.
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