Basic Physics Questions and Answers

A sample of HCl gas is placed in a uniform electric field of magnitude 3 x 104 N C The dipole moment of each HCl molecule is 3 4 x 10 30 Cm Calculate the maximum torque experienced by each HCl molecule Solution The maximum torque experienced by the dipole is when it is aligne perpendicular to the applied field T max pEsin 90 3 4x10 30 3 10

A certain mountain road is inclined 3 with respect to the horizontal The change in height of the car as a result of its traveling 3 km along the road is nearly A 157 m C 116 m B 181 m D 203 m

having resistance 10 is used to find the null point At the null point condition 1 is equal to 0 3 Q2 ww 1 1 O 1 5 V 1 37 5 cm 3 24 cm www 1 2 Q2 41 3 V 6 1 as 03 22171 30 x1 3 1 www 20 Q 2 30 cm 4 45 cm B joined in

The optical power of a thin equiconvex glass lens in air is 10 D Its optical power when surrounded by air on one side and water on the other side and beam of light is incident from air side 4 3 water glass C

ge is set up as shown to determin an unknown resistance X using a standard 1 ohm resistor The galvanometer shows null poin when tapping key is at 52 cm mark The end corrections are 1 cm and 2 cm respectively for th ends A and B The determined value of X is X 3 T 1092 1092cup to zqonb M stwa zi 20 0 8 B2 6 to

7 In ancient time the earth was believed to be a flat disc of uniform thickness Here we adopt the same model and describe the earth as a flat disc of radius sufficiently large say more than 40000 km Mass density is uniform and is equal to p The disc rotates about a stationary axis through its centre and perpendicular to its plane Period of rotation equals one earth day Universal gravitational constant is G The centre of the disc is the North Pole and circular edge is the South Pole All radial lines on the disc are the longitudes and all concentric circles are the latitudes Direction along a latitude in the direction of rotation is the East a If acceleration due to gravity at the North Pole is go what should thickness of the disc be b A shell is fired from the ground with velocity u at an angle with the longitude containing the place of firing How far from this longitude will the shell hit the ground c A shell is fired from the ground with velocity u at an angle with the latitude containing the place of firing How far from this latitude will the shell hit the ground

Knowledge Sections Q No 40 The purpose of adjusting nut in a micrometer screw gauge is to A Take care of zero error B Impart slow motion C Compensate for wear between screw and nut D Take care of backlash

A smooth sphere of mass m is moving on a horizontal plane with a velocity u 3icap jc ap m s when it collides with a vertical wall which is parallel to the vector 3icap jcap I f the coefficient of restitution between the s pheres and the wall is 0 5 find the followin g a Velocity of the sphere after the impact b Loss in kinetic energy caused by the imp act c Impulse J that acts on the sphere

39 Average life of a radioactive sample is 4 ms Initially the total number of nuclei is No A charged capacitor of capacity 20 F is connected across a resistor R The value of R such that ratio of number of nuclei remaining to the charge on capacitor remains constant with time is a 100 c 300 b 200 S d 400 S

Knowledge Sections Q No 23 The phenomenon shown by a measuring instrument which gives different indications in a series of measurements of the same value of the quantity measured is called A Repeatability of measuring instrument B Error of repeatability C Dispersion of indications D Error of trueness

In an induction coil the coefficient of mutual inductance is 4 henry If a current of 5 ampere in the primary coil is cut off in 1 s the e m f 1500 at the terminals of the secondary coil will be 15 kV B 60 kV 10 kV L D 30 kV A C

Q No 24 The quality of a measuring instrument which characterises the ability to respond to small changes of the quantity measured is called A Discrimination of a measuring instrument B Response of a measuring instrument Knowledge Sections C Accuracy D Precision

27 A calorie is a unit of heat and it equals to 4 2 joule We employ a system of units in which the unit of mass equals 4 kg unit of length equals 2 m and unit of time equals 2 second Find the value of 1 calorie in this new system of units 5

28 An equation is given here P a 0 0 1 ML 5 T 1 2 ML5 T 3 ML5 T 2 where P Pressure V Volume and 0 Absolute temperature If a and b are constants the dimensions of a will be

A circular ring of radius R with uniform positive charge density per unit length is located in the YZ plane with its centre at the origin O A particle of mass m and positive charge q is projected from the point P R 3 0 0 on the positive X axis directly towards O with initial velocity v Find the smallest non zero value of the speed y such that the particle does not return to P

A ball dropped from a certain height falls in the influence of uniform gravity strikes the ground and repeatedly rebounds elastically During a time interval of At 8sec from it was dropped it covers a distances 20m How many collisions during this time did the ball make with ground Take g 10m s neglect all resistance

15 20 tan 0 0 1 Let the resulta 0 tan 0 75 36 Thus the resultant of two new forces P an and angle between them is 36 52 EXAMPLE 161 Person Walks in Different Directions A person walks in the following pattern 3 1 km North then 2 4 km West and finally 5 2 km South i Sketch the vector diagram that represents this motion ii How far the person will be from its initial point iii In what direction would a bird fly in a straight line from the same starting point to the same final point Label the displacement vectors A B and C and denote the result of their vector sum as r now choose East as the i direction x direction and North as the j direction y direction All distances are understood to be in kilometres yectors B and C are taken as negative because 7 to our assumption person walks in x and y

4 What will be the dimensions of a b in the relation E b x2 at where E is energy x is distance and t is time 5 In the relation h 2Tcos a r2pg where h is the height T is surface tension p is density and r is the radius of a capillary tube a is angle of contact and g is acceleration due to gravity Verify the correctness of the equation 6 Give one example each of physical quantities which have SI unit but no dimensions which neither have unit nor dimension 7 Acceleration due to gravity is 10m s2

Q No 30 The axis of measurement of the scale or other dimensional reference should coincide This principle is called the A Principle B Principle of alignment C Principle of linear measuring instruments D Principle of collinearity of kinematic design

a attached to 41 Two point masses of 3 kg and 6 kg are opposite ends of horizontal spring whose spring constant is 300 Nm as shown in the figure The natural vibration frequency of the system is approximately 7777 a 4 Hz 6 kg 1 k 300 Nm 1 ooooooo b 3 Hz 3 kg d 1 Hz c 2 Hz the length of the spring

Sections Q No 31 Pick out the wrong stateinent about flexible strips A These are used in instruments where small movements are required between component parts B No force or torque is required to displace a member located on flexible strip from its mid position C It has no friction or backlash D It is not subjected to wear

3 Rocket engines lift a rocket from the earth surface because hot gases with high velocity a react against the rocket and push it up b push against the air c push against the earth d heat up the air which lifts the rocket Rocket give action 100 If a cyclist moying with a speed of 4 2m s a level road can take a sharp circular fun of radius 4 m them ethicient on on a ard friction L between between the cycle tyres and road is

Knowledge Sections Q No 14 Which of the following refers to parasitic error A Error often gross which results from incorrect execution of measurement B Algebraic difference between the results of measurement and the value of comparison C Error which varies in an unpredictable manner in absolute value and in sign when a large number of measurements of the same value of a quantity are made under practically identical conditions D Disagreement between the result of measurement and the value of the quantity measured 7

Knowledge Sections Q No 32 The least count of a metric vernier caliper having 25 divisions on vernier scale matching with 24 divisions of main scale 1 main scale division 0 5 mm is A 0 05 mm B 0 01 mm C 0 02 mm D 0 001 mm

Q No 7 Knowledge Sections Precision of measuring equipment is A The closeness with which a measurement can be read directly from a measuring instrument B A measure of how close the reading is to the true size C The difference between measured value and actual value D The smallest change in measurand that can be measured 5

Given below are plots of Maxwell s distribution of velocity of gas at different temperatures Identify the true relation T No of Molecules OTA TBTC O TA TB TC O TA TB TC OTA TB TC Velocity

In a new system of units energy E density d and power P are taken as fundamental units then the dimensional formula of universal gravitational constant G will be 1 E d 2p2 3 E d p 2 E 2d p 4 E d 2P 2

Two blocks A B having mass ratio 2 1 are lying on a rough surface The friction coefficient between B and ground is 2 and between A and B is u Now a variable force is applied on A at t 0 The mass of block B is m Find the value of time till they move together A mg a C 3 mg a B 2 mg a WZ A D 6 mg a F

B D List 1 D P P D Isothermal B Adiabatic curve 2V B isothermal curves 2V Adiabatic curve Adiabatic curve Isothermal curve 1 P AQcycle 0 List II Q AQcycle 0 R S W cycle 0 W cycle 0

9 A wire of resistance 12 m is bent to form a 1 complete circle of radius 10 cm The resistance between its two diametrically opposite points A and B as shown in the figure is A a 0 6 Q c 6TQ B b 3Q d 6 Q

5 Which of the following is not correct about wavelength standard Slove reruer A Wavelength of monochromatic light is an invariable unit of length B Wavelength standards are a physical standard C It is a reproducible standard D It is a natural unit of length

6 Which of the following is incorrect about micrometer A Thimble and barrel should have a dull finish B Total travel to the measuring spindle is called measuring range C Graduated surface diameter of barrel should be 5 mm D Screw has 10 or 20 threads per cm

172 Which of the following incorrect regarding the motion in a plane 1 A body can t move on a curved path with constant acceleration statement s is are 2 The angle between acceleration and velocity can be 90 3 The angle between acceleration and velocity can be other than 90 All of the above

3 Tower cranes are a common fixture at any major construction site They re pretty hard to miss They often rise hundreds of feet into the air and can reach out just as far The construction crew uses the tower crane to lift steel concrete large tools like acetylene torches and generators and a wide variety of other building materials A crane stands on a level ground It is represented by a tower AB of height 24 m and a jib BR The jib is of length 16 m and can rotate in a vertical plane about B A vertical cable RS carries a load S The diagram shows current position of the jib cable and load 24 m TRIST 16 m R 8 m S Now the jib BR has been rotated and the length RS is increased The load is now on the ground at a point 8 m from A What is the angle through which the jib has been rotated a 15 b 25 c 30 d 45 What is the length by which RS has been increased a 8 3 m b 8 3 2 m c 8 3 1 m d 4 3 2 m DEMY

A particle moves on a circle of radius 3 meters and completes 3 revolutions in 12 seconds Assuming it moves with constant angular velocity find its angular speed A 3 rad s B x rad s C 2 rad s D 2 3 rad s

The figure shows a ray incident at an angle i If the plot drawn shown the 3 variation of r i versus k r angle of refraction H A the value of k is C the value of 0 H 2 3 3 r il B the value of 0 FI 6 D the value of k isl

The moment of inertia of a uniform disc of mass M and radius R about an axis passing through its edge and perpendicular to its plane is 1 Its moment of inertia abou its diameter will be 1 1 2 3 I 12 14 10

A projectile has a maximum range of 16 km At the highest point of its motion it explodes into two equal masses One mass drops vertically downwards The horizontal distance covered by the other mass from the time of explosion is a 8 km c 24 km b 16 km d 32 km 2019

A space capsule is in a circular orbit of about the earth A short burst from a rocket in the backward direction increases the kinetic energy by 20 and causes the capsule to enter ar elliptical orbit with the point of firing as the perigee ier r Then choose the correct statement s for further motion of capsule Assume mass of capsule to remain nearly constant B Total mechanical energy of capsule decreases Time period of capsule will decrease Distance of apogee from centre of earth is r 1 5 If mechanical energy before the event short burstis final mechanical energy after the YOU MARKED YOU MARKED

A point charge of magnitude 1 c is fixed at 0 0 0 An isolated uncharged spherical conductor is fixed with its centre at 4 cm 0 0 The potential and the induced electric field at the centre of the sphere is X 1 1 8 105 V and 5 625 106 V m 3 2 25 x 105 V and 5 625 x 106 V m 2013 2 0 V and 0 V m 4 2 25 x 105 V and 0 V m

4 i Apply Gauss law to show that for a uniformly charged spherical shell the electr field inside the shell vanishes whereas outside it the field is as if all the charge were concentrated at the centre

In U238 ore containing Uranium the ratio of U234 to Pb206 nuclei is 3 Assuming that all U23 ore the lead present in the ore is final stable product of U238 Half life of U238 to be 4 5 x 10 years and find the age of ore is A 10 years Find A rounded off to closest integer

An object is placed in front of a concave mirror The distance of object from the focus is 10 cm and the distance of the image from the focus is 40 cm Then the focal length of the mirror is 1 20 cm 2 10 cm 3 40 cm 4 30 cm

A ball of mass 0 3 kg is tied to one end of a string 0 8 m long and rotated in a vertical circle If the tension in the string be 2 N at the highest point of the circle the tension at the lowest point in this situation will be equal to 2 2 94 N 4 19 64 N 1 0 3 17 64 N

What are the factors on which drift velocity and mobility of free electrons in a conductor may depend on Starting from basic concept prove that resistance of a current carrying conductor is m I ne t A Where the symbols have their usual significance R 3 marks

167 If a charging source supplies charges at constant potential V then work done by the charging source is W qV and energy stored in the charged conductor is U qV Remaining qV energy is wasted as 1 Heat 2 Light 3 Sound 4 All of these

In a mixture of gases the average number of degrees of freedom per molecules is 6 The rms speed of the molecule of the gas is c The velocity of sound in the gas is O ou 20

1 AI A H T B x FIGURE 3 20 Two cells of emf s and in the series 7 7 are their ternal resistances For connections across A and C the combinatio can be considered as one cell of emf and an internal resistance r eq 1 E2 H T E eq E 12 and r F 1 12 eq C VACE IT eq Ir G2 12 Comparing the last two equations we get heline DUAL CAMERA Consider first two cells in series Fig 3 20 where one terminal of by Sourcadeo is joined together leaving the other terminal in either cell Physics Eeq A I If we wish to replace the combination by a single cell between A and C of emf and internal resistance r we would have eq eq Teq 3 63 3 64 3 65 In Fig 3 20 we had connected the negative electrode of the first to the positive electrode of the second If instead we connect the two negatives Eq 3 61 would change to VBC E2 Ir and we will get 2 CO

In an LCR circuit the resonating frequency is 500 kHz If the value of L is doubled and value o C is decreased to 1 times of its initial values ther 8 1 the new resonating frequency in kHz will be 1 250 2 500 3 1000 4 2000

27 When a resistance of 20 22 connected in parallel with a galvanometer then its deflection reduces from 50 divisions to 10 divisions the resistance of galvanometer is 1 80 Q 3 40 Q 2 100 S 4 50 Q