PHYSICS ANSWERS - SHORT ANSWER QUESTIONS (HC VERMA - TEXT BOOK) CH-1 (INTRODUCTION TO PHYSICS) 3
3
1. Because speed of light is equal to = 299,792,458 m/s. 2. (a) [L ] (b) [L ] (c) Dimensionless 3. No, Yes, We can’t measure with any manner
4. Yes, No
5. No
6. Only easily available feature is present.
7. (a) By measuring thickness of 50 paper by vernier callipers (b) by using keplar’s law.
CH-2 (PHYSICS & MATHEMATICS) 1. No
2. No, Yes
3. No
4. Yes, Yes
6. (a) Most proper
7. No, Yes
8. Yes
10. No, Yes
11.
5. Yes, like current
ˆ ˆ - 4jˆ , 4iˆ + 3j,4i ˆ ˆ - 3jˆ 12. No, still it is not possible because a vector can not be equal to a scalar.. -3iˆ + 4j,3i
13. No
14. Yes, No
CH-3 (REST AND MOTION: KINEMATICS) 1. Equally wrong
2. These are equal in magnitude 3. No, we can not compare only magnitude of two vectors.
-1
v(ms ) 20 2
4
0
4.
t(s)
5. Motion under gravity
6. At its highest point
7. Particle B
8. No
–20
9. 10. 11. 13.
Straight line if aeroplane is going with constant velocity. Parabolic, (real path is useless). (a) In motion under gravity it is at highest point. (b) Projected particle in vertical direction under gravity (c) In uniform circular motion. t=t1 ®v (+), a(+), t=t2®v(0)a(–), t=t3 ®v(–) a(+) 12. Both have equal displacement Yes, by changing the direction or applying the break. 14. Speed of light does not depend on reference frame.
CH-4 (THE FORCES)
13678-
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9-
E
10-
Force mg applied on earth by object. 2- Contact force between boy and chair, Contact force between chair and floor, Gravitational force between earth and boy, Gravitational force between chair and earth. Not of any type. It is only mental torcher. 4- Electro magnetic force 5- Yes (a) 15 (b) 3.6 (c) 0.36 (d) 0.036 Contact force of floor & block A, Gravitational force of earth. (a) Weight of pulley, contact force of string, contact force of clamp. (b) Weight of boy, contact force of surface, tension force of string. (c) Weight of block, Tension force of string. Weight, contact force, tension force, weight of trolly & person, contact force between trolly & person & surface, tension force among person, trolly & person is according to newton’s third law. Force Force by which Nature of force Direction On motor
1- By horse 2- By surface 3- By surface 4- By person 5- By earth
Electro magnetic Electro magnetic Electro magnetic Electro magnetic Gravitational
Forward Upward Back ward Down ward down ward 1
IIT - JEE On horse
1- By person 2- By motor 3- By surface 4- By surface 5- By earth
Electromagnetic Electromagnetic Electromagnetic Electromagnetic Gravitational
Back ward Back ward For ward Up ward Down ward
On driver
1- By horse 2- By motor 3- By earth
Electromagnetic Electromagnetic Gravitational
For ward Up ward Down ward
CH-5 (NEWTON'S LAWS OF MOTION)
15-
Yes, No
2- Zero, yes
3- Straight line, Rest
Inertia of motion
6- Yes
7- Yes
8-
æ 2m1m2 ö (a) 20 kg weight (b) No (c) then reading is ç 9- No è m1 + m2 ÷ø
11-
Due to increase in contact time, injury is less.
12-
One team will win because of getting more force by floor.
13-
Buoyancy force
16-
14- No, act on a same object
4- Yes, Yes
10- Friction force
15- Yes, No
17- No, by dropping a coin.
Yes, We can define it by pseudo force.
CH-6 (FRICTION) 1-
Not necessary
2-
Due to less normal reaction, friction force is less.
3-
Zero
4-
Due to less coefficient of friction
5-
6-
No, No
7-
(a) Less (b) Heavy (c) Due to inertia of rest
8-
Due to less pushing force. No
9-
Due to more normal reaction by contact surface 10- By throwing the bag with the help of newton’s third law.
11-
Due to cold welding
CH-7 (CIRCULAR MOTION)
1- Yes, By applying break or turning 2- The centrifugal force will dry the cloths for the person sitting on the drum & the centripetal force will dry the clothes for person who is washing the clothes.
3- By friction force 4- By normal reaction 5- No 6- Due to inertia of rest 7- Outer 8- (B) 9- By applying break 10- Tension will be more during oscillation. CH-8 (WORK AND ENERGY)
1- No 2- No 3- Yes, work depends on the position of observer. 5- Yes, person moving up in an elevator 6- Yes, internal energy converts into kinetic energy. 7- Yes 8- No, No 9- Potential energy is a reference dependent quantity. 10- Yes 11- Positive, Negative 12- (a) Positive (b) Negative (c) Zero (d) Negative (e) Positive 13- Decrease 14- Work done by you converts in it. 15- Velocity can be changed but speed not. 16-
(a) Ki = 2
1 1 2 2 mv0 , (b) Kf = 0, Wk.f. = – mv0 2 2
17. (a) Ki =0, Kf = +
1 1 2 2 mv0 (b) + mv0 2 2
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4. Work done by the static friction force on the person travelling in bus w.r.t to observer standing on ground.
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PHYSICS CH-9 (CENTRE OF MASS, LINEAR MOMENTUM, COLLISION)
1- Yes 2- Yes 3- Yes 4- (a) Yes
(b) Yes (c) No 5- No 6- No, Tension force 7- Due to high friction force
8- Yes 9- No
10- Yes, Yes, No 11- No, No 12- Yes, No, only magnitude of net momentum can be calculated 13- Yes, less than
r 2
14- Yes, if not completely closed 15- Centre of mass does not shift. 16- Yes 17- Possibility of falling of forward person is high. 18- No. 19- Yes 20- No 21- Friction force 22- Ground reaction force 23- In b particle emission, a neutrino particle is also emitted due to this momentum is conserved. 24- Go back side in van.
25- No. CH-10 (ROTATIONAL MECHANICS)
1. No 2. Yes, line perpendicular to the plane of motion of pendulum passing through the suspension point. 3. No
4. Yes, Yes
5. No, Yes
6. No
8. 0.5 mg, yes
9. No
10. No, Yes
11. No
12. No
13. No
14. Torque of weight
16. Near to upper end
17. Yes, No, Normal shifts
18. End B 19. Yes 20. Duration increases 21. Ring
7.No, Yes
22. Yes
CH-11 (GRAVITATION)
1- No, No, Yes
2- No
3-
F M
6- Equal weight
7- Apple
8-
-
¾ Constant 4- No
2k r3
5- Moon also rotates around the sun.
9- Yes, No, we should use
U=-
Gm1 m2 + 20 r
10- Yes, if we use spring balance. 11- Real weight, No 12- Increases 2% 13- No, rotate with satellite, Astronauht should bring the bolt with him. 14- Yes 15- No, Yes 16- No 17- mg > mw2 r 18- No, rotating satellite from east to west. 19- The neutral point is near the moon and away from earth. CH-12 (SHM)
1- No, because entire routine of the person will not be repeated in exact fasion. 2- No 3- Yes, No 4- Amplitude, zero 5- Yes 6- Speed will be high on point P .This will not disappoint us. 7- It is easy to locate lowest point. 9- Yes, Yes 10. (B) 11- It will gain time because time period will decrease 12- No 13- Increase then decrease 14- Yes 15- Marching frequency comes in resonace with bridge frequency. 16- Simple harmonic motion CH-13 (FLUID MEACHNICS)
f , Area of the needle is less than the contact area of rod A 3. As density of the liquid will be variable 4. Less than the actual difference. No 5. Yes, Yes, No. liquid surface will be r r perpendicular to the effective ‘g’ is = geff = g - w2 R 6. Length will be more than 76cm but height will be same that
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1. No, sepration between the molecule may differ 2. P =
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of 76 cm. 7. No. it can only rise upto a height of 76 cm. 8. Effective g is zero therefore height will be 1m. 9. No. as pressure outside the tube is greater than pressure inside the tube 10. Yes, No. 11. Density of sea water is greater than density of fresh water therefore buyont force is greater. 12. No 13. Rock should removed from the boat. 14. Velocity of water increases due to fall in potential energy in result of this area of cross section reduces 15. Due to increase in the velocity of water stream due to reduction of area. 16. Due to reduction of pressure outside the convas by bernoullis theoram. 3
IIT - JEE CH-14 (PROPERTIES OF MATTER) 1. First decreases upto an extent 2. Librated in form of heat 3. Thicher bones reduces the stress 4. Much less than the 1% 5. Absorbed by the rubber sheets 6. Difference in the internal energy of the acid 7. Force due to surface tension is only acts on the free surface of liquid. 8. Adhesive force decreases. 9. Neither rises nor fall it will remain at same level. 10. No. 11. No Adhesive force does not acts on bulge portion to reduce surface energy it will acquire a shape of sphere. 12. No 14. Due to sticly wings to reduce surface energy 15. Projected force due to pressure is in the direction of force due to surface tension 16. Yes 17. No. 18. Due to viscous force on the liquid 19. Costor oil due to high viscosity.
CH-15 (WAVE MOTION AND WAVES ON A STRING)
1-¥
No
2-¥
3-¥
5-¥
Energy will be in form of potential energy.6. No.
Non-mechanical
7-¥
Negative -x
VP V
4.
8-¥
1.5p
2pA A < 1 = l æ l ö çè 2p ÷ø
= -wA = max
No, Yes
CH-16 (SOUND WAVES)
1- No, No 2- No, No 5- Mass of He is less than that of air.
3- (A) Longitudinal
4. Heared
(B) Transverse
7. Tunning fork of double frequency has high intensity
8. Yes
CH-17 (LIGHT WAVES)
1. For same medium colours will be different, No, infinite 2. No 4. The wavelength of sound is equivalent to dimension of obstacle so due to diffraction sound waves is very less as compare to obstacle. So it does not diffractex. 5. The earth is round and light waves moves in straight line there fore TV. Signals can not send straight from Delhi to Patna. 6. Yes,10 cm, sound intensity 7. No, Yes (because contrast is maximum for same intensity) 8. No 9. The interference can not be observed from candles due to non coherent source. The interference can be done by Laser source. lD ö æ 10. Fringe width ç b = is decreased on increasing d. The fringe pattern will disappear on increasing d too much. è d ÷ø
1. No
2. No
3. Due to internal refraction
4. Fluctuating image
5. Yes
6. No, Yes Yes
7. Yes
8. Large field of view
9. Slow
10. Long
12. No
13.No
14. Diversing lens
18. No
19. No
15.
16. No
f1
17. Yes
f2
CH-20(DISPERSION AND SPECTRA) 1. No, No
4
2. No, Positive 3. No
5. Yes, No
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CH-18 (GEOMETRICAL OPTICS)
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PHYSICS CH-23 (HEAT & TEMPERATURE) 1.Yes
2. No
3. Yes, because heat is proportional to temperature
4. Experiment containing a barometer and a closedd vessel to be heated. 5. No 6. Due to abnormal behavior of water near at 4°C. 7. No
8. No
9. No
10. The lid will expand due to increasing temperature. 11. Quenching does not take place if water should be put showly 12. Yes
1 3. He re volume in dicates the volume occupied by the spheri cal shel l.
CH-24 (KTG) 1. Yes, No
2. Due to the gases in form of liquid state 3. No
4. No, No
5. This statement is wrong but macroscopically the temperature is same. 6. Yes 8. There will be no motion.
7. No
9. You can not determine pressure, density and average kinetic energy.
10. Charle’s law is valid for constant mass. 11. Due to increasing pressure, boiling point will increase. 13. Yes, No 14. Due to increasing vaporization.
12. More vaporization
CH-25 (CALORIMETRY) 1. No
2. This is a fact
3. To isolate the system
4. Yes till flow of energy.
5. To increase the contact time and area 6. In changing state 8. Internal energy of vapour is more
7. (a) Infinite (b) Infinite
9. Water takes more time to be hot & to cool.
10. Low specific heat.
CH-26 (LAWS OF THERMODYNAMICS) 1. No
3. mgh, 0, No] No
2. Yes
6. No (Mechanical work)
7. No, Yes
4. Fd, No
8. No, No
11. Cooling due to adiabatic expansion. 14. Temperature of sink will be zero kelvin
5. Heat 9. Yes
12. Yes, No 15. Yes, No
10. No
13. No
CH-27 (SPECIFIC HEAT CAPACITIES OF GASES) 1. No, No (Infinite)
2. No (¥) 3. No, (zero)
4. CP is slightly greater then CV.
5. CP –CV > R
6. Yes, Free expansion in insulating system of ideal gas
8. No, No
9. No
2
2
2
10. f = g - 1 = 1.29 - 1 = 0.29 = 6.89 = 6
CH-28 (HEAT TRANSFER)
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1. Because this is not a continuous process. it has quantum nature.
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2. Yes, But it absorbs much.
3. Convection currents, No,No 4. No
7. Due to forced convection
8. Due to low pressure
5. Wooden chair
9. No
6. Yes, Yes
10. Clouds reflect the energy
11. White dress has low absorbing power.
CH-29 (ELECTRIC FIELD AND POTENTIAL)
1- No.
2- Yes
3- Yes, Yes
6- No
8- No
9- No, path will be according to position
12- The length of dipole w.r.t.
4- No
5- Due to charge generated by friction
distance of observer from centre.
10- 1%3
11- No
13- Due to free electrons
14- No, total charge will zero 5
IIT - JEE CH-30 (GAUSS'S LAW)
1- Maximum when electric field is perpendicular to surface, minimum when parallel. 2- Yes, flux i.e. number of electric lines remain same. 3- Zero, if conductor is spherical shell then remain unchanged, Yes 4- Zero, Yes if shell is conductor then field is zero. 5- No 6- No 7- No, No, No CH-31 (CAPACITORS)
Q1 - Q2 2. No 3. Both of them have equal potential 4. 0] 0] The whole positive charge will come on the outer 2 surface. 5. No, the knowledge of potential is also necessary. 7. Attraction
1.
CH-32 (ELECTRIC CURRENT IN COUNDUCTORS) 1. 10W, 45W, 90W 2. Yes ] East to west 3. Yes ] left to right 4. Forward to backward 5. Drift velocity is a average quantity. 6. Electric field in cunductor is zero at electro static equilibrium position. If potential is applied the electric field will be non-zero. 7. No 10. No
11. No
8. Due to less resistance
9. U µ i2
12. No, yes 14. Charge 15. Potentiometer16. No
17. Yes
CH-33 (THERMAL AND CHEMICAL EFFECT OF ELECTRICAL CURRENT) 1. The resistance will increase due to increase in temperature with time therefore current decreases with time. 2.Yes, r = R1R 2 3.No
CH-34 (MAGNETIC FIELD) 1. Yes, No 2. Yes, Yes time varying magnetic field exists.3. No, if magnetic field is uniform then only it will be zero. r 4. Yes, No 5. If it enters tangentially 6.Yes] kˆ 7. Yes, if plane of loop is perpendicular to B 8. Magnetic field only exerts force on moving charge i.e. electron. 9. For stable equilibrium q = 0° 10. Rate of change of flux gives emf
CH-35 (MAGNETIC FIELD DUE TO A CURRENT) B=
1- Vertically upward, vertically downward, due west, due east
2.
3. Going away from osberver 4. No
7. No
6. Yes, Yes
m0 2p
i d
=
i 2pd Î0 c2
é êC = ë
1
ù m0 Î0 úû
8. Force and torque both work on it.
9. The electrostatic force is greater than magnetic force, while electric force on current element is zero. 10. Yes
11. Magnetic field of on wire cancel out by another wire. 12. Magnetic force does not work on point
charge. 1.
No] Flux f is constant w.r.t time.
2.
DI Will be maximum when switch is open because time interval is very less. DT
3. 4.
To prevent the change in flux Eddy currents will be generated in coil which opposes the oscillatory motion of coil. According to Lenz’s law, the changing flux exerts force on magnet.
5.
Yes, When the current in first loop changes till current will induced in second loop. Loop will repel each other.
6.
Yes, There is a change in current till current will be induced. Loop will attract.
7.
In the box change in magnetic field is very less.
9.
Induced eddy current opposes the motion.
11. (a) Plane of both loops are parallel. (b) Plane of both loops are perpendicular 12. On centre 6
13. On centre
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CH-38 (ELECTROMAGNETIC INDUCTIONS)
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PHYSICS CH-39 (ALTERNATING CURRENT ) 1. Infinite 2. Zero 3. Same 4. Yes 5. Yes, This is according to ohm’s law 6. The rms value of current will increases because Irms = Vwc 9.
7. No
8. No
i20 R i 20 R , ,0, The theory of superposition will obey current while not for heat energy 2 2
10. No 11. The impedance will more when applying AC . If we apply DC the transformer will burn becan be of high current. 12. No, No
13. Decrease, may decrease or may increase
14. Yes, No
CH-42 (PHOTOELECTRIC EFFECT AND WAVE-PARTICLE DUALITY) 1. No 2.No 3. (a) c (b) c 4.No, No 5. Number of photons will be decreased if room is maintained at a constant lower temperature. 6. No, energy of a photon can’t be called its KE or IE. 7. No 8. Green light 9. Every photon should be capable to start photo synthesis 10. Metal gains positive charge which stops furthur emission of photoelectrons. 11. No 12. (a) proton (b) equal (c) proton 13. No, there is no colour of matter (probale) waves.
CH-43 (BOHR’S MODEL AND PHYSICS OF THE ATOM) 1. Infinite, infinite 2. Yes, (13.6)
Z2 = (–13.6) Þ Z=n 3. Lyman Series (Absorption transitions can only occur from n2
n=1 to n>1) 4. At room temperature, hydrogen atoms is in ground state. 5. Balmer series lies in the visible range of the spectrum 6. P.E. + K.E. = T.E. Þ –P.E.+
|P.E|ù é ê as K.E. = 2 ú ë û
P.E. = T.E. 2
Þ T.E. = -
P.E. 2
Potential energy of first state is –27.2eV when infinity is considered at 0 eV therefore if will beat –17.2eV when infinity is considered at 10eV. Þ P.E. + K.E. = T.E. Þ –17.2 + 13.6eV = T.E Þ T.E. = 3.6 eV
é1 1ù 7. hv = 13.6 ê 2 - 2 ú for limit of by mans series [n 1 = 1, n2 = ¥] n n ë 1 2û é1 1 ù v = constant ê - ú ë1 ¥ û
...(1)
é1 1 ù v = constant ê - ú ë4 ¥û
...(2)
for limit of balmer series [n 1 = 2 ; n2 = ¥] By subtrating (1) and (2) we get first line of lyman 8. Ability to work is energy = qDv, Ionization energy = eU (Ionization potential) For some other unit it will not hold true. 9. Yes 10. Yes, Yes
CH-44 (X-RAYS)
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1. KE of incident electrons 2. No 3. Yes 4. Yes 5. No 6. No 7. Yes 8. Yes 9. No, due to low energy gap between energy levels. 10. X-ray photons are more energetic
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CH-46 (THE NUCLEUS) 1. As neutron is an unstable particle 2. Yes, nuclear force is spin dependent 3. Nuclear force is a short range force. 4. Carbon, lead 24 5. Mg 6. Generation of cathode rays is an atomic phenomenon and generation of b-rays is a nuclear phenomenon we can differentiate on the basis of their energy. 7. From extrenally supplied energy.
8. Yes
9. 73 Li
10. Yes
11. Lighter, same
12. Electrostatic repulsion prevents their fusion. 7
