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CAREER POINT

PRACTICE PROBLEM SHEET

PHYSICS

Topic Nuclear Physics & Radioactivity-1

Q.1 A star of mass M0, radius R0contracts to radius R. Energy radiated by the star assuming uniform density in

each case while temperature remains unchanged is -

(1M0c! (! M0c

!

!

0

"1R

R(#M0c

!

0

"1R

R($M0c

!

#

0

"1R

R

Q.2 %he total energy E of a sub-atomic particle of rest mass m0 mo&ing at non-relati&istic speed

& is -

(1E' m0c! (!E'

!

1m0&

! (#E' m0c!

!

1m0&

! ($E' m0c!"

!

1m0&

!

Q.3 )f udenotes 1 atomic mass unit. *ne atom of an element has mass e+actly eual to Au, where A is mass

number of element -

(1A' 1 (!A' 1!

(#A' 1 ($ A can tae up any integral &alue from 1 to 110

Q.4 /ast neutrons can easily be slowed down by -

(1 the use of lead shielding (! passing them through hea&y water

(# elastic collisions with hea&y nuclei ($ applying a strong electric field

Q.5 hich of the following statements is correct -

(1 eta rays are same as cathode rays (! 2amma rays are high energy neutrons

(# Alpha particles are singly ioni3ed helium atoms ($ 4rotons and neutrons ha&e e+actly the same mass

Q.6 Mar the correct statement -

(1 E&ery element has only two stable isotopes

(! All isotopes of e&ery element are radioacti&e

(# *nly one isotope of each element is stable

($ 5uclei of different elements can ha&e the same number of neutrons

Q. %he chemical beha&iour of an atom depends upon -

(1 the number of nucleons in its nucleus (! the number of protons in its nucleus

(# the number of neutrons in its nucleus ($ the number of electrons in its atom

Q.! 6uring a nuclear fusion reaction 7CAREER POINT, CP Tower, IPIA, Road No.1, Kota (Raj.), Ph: 0744-3040000 1

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(1 a hea&y nucleus breas into two fragments by itself

(! a light nucleus bombarded by thermal neutrons breas up

(# a hea&y nucleus bombarded by thermal neutrons breas up

($ two light nuclei combine to gi&e a moderate nucleus and possibly other products

Q.# oron rods in a nuclear reactor are used to -

(1 absorb e+cess neutrons (! absorb alpha-particles

(# slow down the reaction ($ speed up the reaction

Q.1" hich of the following statement (s is (are correct 8

(1 %he rest mass of a stable nucleus is less than the sum of the rest masses of its separated nucleons.

(! %he rest mass of a stable nucleus is greater than the sum of the rest masses of its separated nucleons.

(# )n nuclear fusion, energy is released by fusing two nuclei of medium mass (appro+imately. 100 amu

($ 5one of these

Q.11 9et mpbe the mass of a proton, m

nthe mass of neutron, M

1the mass of a

105e!0nucleus and M

!the mass of a

!0:a$0

nucleus. %hen -

(1 M!' !M

1(! M

!; !M

1(# M

!< !M

1($ M

1< 10 (m

n m

p

Q.12 *rder of magnitude of density of =ranium nucleus is,>mp' 1.? @ 10"!?g

(1 10!0gBm# (! 101?gBm# (# 101$gBm# ($ 1011gBm#

Q.13 inding energy per necleon &ersus mass number cur&e for nuclei is shown in the figure. , C, D and are

four neclei indicated on the cur&e. %he process that would release energy is 7

(1 D! (! C (# !D ($ C ' D

Q.14 )n a star all Felium nuclei are con&erted into o+ygen. )f atomic mass of MFe

' $.00!= and atomic mass of

o+ygen M0' 1G.HHH$=, then the reaction energy per atom of o+ygen -

(1 10.! MeI (! 0 MeI (# G.!$ MeI ($ !0.$ MeI

Q.15 %he nucleus of element C (A ' !!0 undergoes -decay. )f J-&alue of the reaction is G.G MeI, then

appro+imate inetic energy of -particle is -

(1 G. MeI (! G.$ MeI (# $.H MeI ($ .G MeI

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ANSWERS$

1.%4 6ensity of star of mass M0, radius R0 is '

#0

0

#

$R

M

*n contracting the new mass becomes

M'#

$R#'M0

#

0

R

R

9oss in mass due to contraction ' " M

Loss = M0 M

Energy radiated ' c!M

2.%3 E' mc!

E' m0c!

!B1

!

!

"1

c

V

Kincec

&