a body of mass 3kg moving with a velocity (i+2j+3k)m/s collides with another body of mass 4kg moving with a velocity 2i+j+kin m/s they stick together find the velocity of composite body find the kinetic energy before and after collision
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PHYSICS
A body of mass 3 kg moving with a velocity (2
i
^
+3
j
^
+3
k
^
)m/s collides with another body of mass 4 kg moving with a velocity (3
i
^
+2
j
^
−3
k
^
)m/s. The two bodies stick together after collision. The velocity of the composite body is
A .
7
1
(4
i
^
+6
j
^
−3
k
^
)
B .
7
1
(18
i
^
+17
j
^
−3
k
^
)
C .
7
1
(6
i
^
+4
j
^
−6
k
^
)
D .
7
1
(9
i
^
+8
j
^
−6
k
^
)
October 15, 2019
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Abhijeet Perisetla
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VIDEO EXPLANATION
ANSWER
Given - m
1
=3kg,m
2
=4kg,v
1
=2
i
^
+3
j
^
+3
k
^
,v
2
=3
i
^
+2
j
^
−3
k
^
Let v be the velocity of composite body .
As the bodies stick together , hence mass of composite body
m=m
1
+m
2
=3+4=7kg
Now , by law of conservation of linear momentum
total momentum before collision= total momentum after collision
m
1
v
1
+m
2
v
2
=mv
3(2
i
^
+3
j
^
+3
k
^
)+4(3
i
^
+2
j
^
−3
k
^
)=7v
or 6
i
^
+9
j
^
+9
k
^
+12
i
^
+8
j
^
−12
k
^
=7v
or 18
i
^
+17
j
^
−3
k
^
=7v
or v=1/7(18
i
^
+17
j
^
−3
k
^
) m/s