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Test Index
Class 11 NEET Physics System of Particles and Rotational Motion
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© examsnet.com
Question : 36
Total: 109
A force
→
F
=
α
^
i
+
3
^
j
+
6
widehat
k
is acting at a point
→
r
=
2
^
i
−
6
^
j
−
12
widehat
k
. The value of
α
for which angular momentum about origin is conserved is
[NEET 2015]
zero
1
-1
2
Validate
Solution:
👈: Video Solution
From Newton's second law for rotational motion,
→
τ
=
→
d
L
d
t
, if
→
L
=
constant then
→
τ
=
0
So,
→
τ
=
→
r
×
→
F
=
0
(
2
^
i
−
6
^
j
−
12
widehat
k
)
×
(
α
^
i
+
3
^
j
+
6
widehat
k
)
=
0
Solving we get
α
=
−
1
© examsnet.com
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