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JEE Mains Model Paper 13
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© examsnet.com
Question : 5
Total: 90
A stream of neutrons each with a kinetic energy of 0.0327 eV. Half life of neutrons is 350s.The fraction of neutrons which will be present in stream, at an instant when they havetravelled 875 km, is
x
10
. Find x. [Take mass of neutron to be 1.675 ×
10
−
27
kg]
2
4
5
6
Validate
Solution:
1
2
m
v
2
= 0.0327 × 1.6 ×
10
−
19
J
v = 2.5 ×
10
3
m
s
−
1
t =
875
×
10
3
v
= 350 s = half life period
∴ fraction is
1
2
=
5
10
© examsnet.com
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