Ask Questions, Get Answers
Menu
X
JEEMAIN Crash Practice
15 Test Series
NEET Crash Practice
15 Test Series
CBSE XII
Math
JEEMAIN
Math
Physics
Chemistry
Practice Test Series
CBSE XI
Math
NEET
Physics
Chemistry
Biology - XII
Biology - XI
Olympiad class V
Math - 5 Test Series
Olympiad class VI
Math - 5 Test Series
studyplans
JEEMAIN Crash Practice
15 Test Series
NEET Crash Practice
15 Test Series
CBSE XII
Math
JEEMAIN
Math
Physics
Chemistry
Practice Test Series
CBSE XI
Math
NEET
Physics
Chemistry
Biology - XII
Biology - XI
Olympiad class V
Math - 5 Test Series
Olympiad class VI
Math - 5 Test Series
mobile
exams
ask
sample papers
tutors
pricing
login
X
ASK
Home
>>
JEEMAIN and NEET
>>
Physics
>>
Class11
>>
Motion in a Straight Line
$v_A=(x \hat i+6 \hat j) m/s,v_B=(3 \hat i+2 \hat j) m/s$ find x such that the relative speed of A with respect to B becomes 5 m/s
\[(a)\; 3 \quad (b)\;4 \quad (c)\;5 \quad (d)6 \]
jeemain
physics
class11
unit2
kinematics
motion-in-a-straight-line
relative-velocity
medium
Share
asked
Jun 25, 2013
by
meena.p
recategorized
Aug 11, 2014
Please
log in
or
register
to add a comment.
Please
log in
or
register
to answer this question.
1 Answer
$v_{AB}=v_A-v_B$
$\qquad=(x-3) \hat i+(6-2) \hat j$
$\qquad= (x-3) \hat i+4 \hat j$
Speed$=|\bar {v}_{AB}|$
$\qquad=5$
$\qquad=\sqrt {(x-3)^2+4^2}$
$\qquad=>25=(x-3)^2+16$
$\qquad=>x=6\; or \;0$
Hence d is the correct answer.
answered
Jun 25, 2013
by
meena.p
edited
Jan 25, 2014
by
meena.p
Please
log in
or
register
to add a comment.
Related questions
A bus is moving with a speed of $10 m/s$ on a straight road. A scooterist wishes to overtake the bus in $100 s$. If the bus is at a distance of $1 \;km$ from the scooterist with what speed should the scooterist chase the bus?
jeemain
physics
class11
unit2
kinematics
motion-in-a-straight-line
relative-velocity
medium
asked
Jul 3, 2013
by
meena.p
1
answer
A 150 m long train is travelling from West to East at a speed of 20 m/s. A bird is flying from East to West at a speed of 5 m/s above the train. How long will the bird take to cross the train ?
jeemain
physics
class11
unit2
kinematics
motion-in-a-straight-line
relative-velocity
medium
asked
Jun 20, 2013
by
meena.p
1
answer
An elevator car whose floor to ceiling distance is 2.7 m starts ascending with constant acceleration of $1.2 m/s^2$ after 2 seconds of the start a bolt begins falling from ceiling of elevator. What is the time after which the bolt hits the floor of the elevator.
jeemain
physics
class11
unit2
kinematics
motion-in-a-straight-line
relative-velocity
difficult
asked
Jun 27, 2013
by
meena.p
1
answer
Two trains each having speed $30 km/hr$ are leading towards each other on the same straight track. A bird can fly at $ 60 km/hr$ flies off one train when they are $60 km$ apart and heads directly for the other train. On reaching other train it files directly back to first and so on. How many trips can the bird fly from one train to another before the trains crash?
jeemain
physics
class11
unit2
kinematics
motion-in-a-straight-line
relative-velocity
difficult
asked
Jul 2, 2013
by
meena.p
1
answer
An open lift is moving upward with velocity $10 m/s$. It has an upward acceleration of $2 m/s^2$ . A ball is projected upward with velocity $20 m/s$ relative to ground. Find the time when ball meets the lift
jeemain
physics
class11
unit2
kinematics
motion-in-a-straight-line
kinematic-equation-for-accelerated-motion
medium
asked
Jul 3, 2013
by
meena.p
1
answer
An open lift is moving upward with velocity $10 m/s$. It has an upward acceleration of $2 m/s^2$ . A ball is projected upward with velocity $20 m/s$ relative to ground. What is displacement of lift and ball at a time when ball meets the lift.
jeemain
physics
class11
unit2
kinematics
motion-in-a-straight-line
kinematic-equation-for-accelerated-motion
medium
asked
Jul 2, 2013
by
meena.p
1
answer
A body travelling along a straight line traversed one third of the total distance with velocity 4 m/s. The remaining part of distance was covered with a velocity $2 m/s$ for half the time and with velocity 6 m/s for other half of time. the mean velocity averaged over whole time of motion.
jeemain
physics
class11
unit2
kinematics
motion-in-a-straight-line
speed-and-velocity
difficult
asked
Jun 25, 2013
by
meena.p
1
answer
Ask Question
Tag:
Math
Phy
Chem
Bio
Other
SUBMIT QUESTION
►
Please Wait
Take Test
JEEMAIN Crash Practice
15 Test Series
NEET Crash Practice
15 Test Series
JEEMAIN
350+ TESTS
NEET
320+ TESTS
CBSE XI MATH
50+ TESTS
CBSE XII MATH
80+ TESTS
...
X