Basic Physics Questions and Answers

Two identical simple pendulums each of length 1 are suspended from the ceiling Their bobs each of mass m are connected by a very light relaxed elastic cord of force constant k as shown in the figure If the bobs are symmetrically pulled apart slightly and released what is period of the ensuing oscillations a c T 2k g m k 2 g 2 b T d 2k m 2k g 2

Sir according to law of motion Inertia All o bject have property of tendency to keep mo ving in a straight line at a constant speed w hen no force act upon them But speed will decrease when the object ch ange the direction of motion Therefore if th e direction is continuously changing the mo tion of object keep decreaseing and becom e stop Then Why the rotation of earth does not sto D

A student is performing on 230 v dc shunt motor in which he uses an armature resistance of 0 22 ohm and field resistance of 115 ohm At no load motor takes input current of 15 A and at full load it takes 20 A If the motor runs at a speed of 1000 rpm at no load then examine following 1 Evaluate the armature current at no load 2 Calculate the armature current at full load 3 Determine the back emf of dc motor at no load 4 Determine the back emf of dc motor at full load

A straight segment of wire has a length of 11 cm and carries a current of 8 A It is oriented at right angles to a magnetic field of 0 5 T Calculate the magnitude of the magnetic force on the segment of wire The magnitude of the magnetic force on the segment of wire is N

2 131 A thin rod AB of length 3m is pivoted at A so that it can rotate freely about A in a vertical plane Its linear density of mass 2 varies as Kx where K kg m and x is the distance from the end A When the rod is in equilibrium a sharp impulse of 27 N s is given to it at the end B in horizontal direction in the 416 plane of rotation If the force exerted on the rod by the pivot when it becomes horizontal is Newton n then find the value of n A

136 A disc of radius 5cm rolls on a horizontal surface with linear velocity v 11 m s and angular velocity 50 rad sec Height of particle from ground on rim of disc which has velocity in vertical direction is in cm D L

A truncated cone 30 cm high is constructed of aluminum The diameter at the top is 7 5 cm and the diameter at the bottom is 12 5 cm The lower surface is maintained at 93 C the upper surface at 540 C The other surface is insulated Assuming one dimensional heat flow what is the rate of heat transfer in watts

132 In the arrangement shown the rod is freely pivoted at point O and is in contact with the equilateral triangular block which can moves on the horizontal frictionless ground As the block is given a speed v forward the rod rotates about O Find the angular velocity of rod in rad s at the instant when 0 30 Take v 20 m s a 1 m 2a 3

47 A cylindrical steel plug is inserted into a circular hole of diameter 2 60 cm in a brass plate When the plug and the plates are at a temperature of 20 C the the hole The temperature at which the plug will just diameter of the plug is 0 010 cm smaller than that of fit in it is 11x 10 6 C b 20 C Given a steel a 48 C and a brass c 10 C m is er 19 10 C d 458 C

A temperature difference of 85 C is impressed across a fiberglass layer of 13 cm thickness The thermal conductivity of the fiberglass is 0 035 W m C Compute the heat transferred through the material per hour per unit area A truncated cone 30 cm high is constructed of aluminum The diameter at the top is intained

A reactor is developing energy at the rate of 3000 kW How many atoms of U235 undergo fission per second if 200 MeV energy is released per fission A 6 5 x 10 2 B 5 15 x 10 C 3 384 x 1023 D 9 4 x 10 6

In the shown arrangement of hemisphere and rod if hemisphere is moving with velocity 4 m s and one end of rod which is in contact with horizont surface is moving with velocity 2 m s then Hemisphere 2 m s 0 0 Rod dx dt dt Ide dt 6 m s 3 2 rad s when 0 45 4 m s 4 rad s when 0 45 4 m s

Solid A has face centered cubic lattice with the length of the cube a 3 65 Another solid B has a body centered cubic lattice with a 2 90 Calculate the ratio of densities of two solids

A ring of mass m and radius R moves on horizontal plane as shown in the figure The magnitude of angular momentum of the ring about point P is e 3 ZNR O 2mv R O mv R Vo 2V0 Vie

lead tin alloy of composition 30 wt Sn 70 wt Pb is slowly heated from a temperature of 150 00 F a At what temperature does the first liquid phase form b What is the composition of this liquid phase c At what temperature does complete melting of the alloy occur d What is the composition of the last solid remaining prior to complete melting Composition at Sn 60 Temperature C 0 300 200 100 327 C Pb a 20 18 3 20 40 L 183 C 40 a B Liquid 61 9 60 Composition wt Sn 80 80 B L 232 C 97 8 100 B 600 500 400 300 200 100 100 Sn Temperature F

g Which of the following option is correct for the apparent weight Wapp of a body in a lift Given W mg true weight 1 When the lift moves upwards with an acceleration a Wapp Wo 1 1 8 2 When the lift moves downwards with an a app Wo 1 g acceleration a Wa a 3 If lift is retarding upward Wapp Wo 1

1 Suppose the gravitational attraction varies inversely as the distance from the earth if the orbital velocity of a satellite in such a case varies as nth power of distance then n equals 2 Zero 4 2 1 1 3 1

1 A metallic wire of uniform cross section and resistance R is bent into a circle of radiu a The circular loop is placed in a magnetic field B t which is perpendicular to the plane of the wire This magnetic field is uniform over space but its magnitude decreases with time at a constant rate k where The tension in the metallic wire is a k 2R c b B t k R B t 2 a k R d poro B t k dB t dt

The sum of magnitudes of two forces acting at a point 16N If the resultant force is 8N and its direction perpendicular to smaller force then the forces are 6N 10N 2 8N 8N 1

Oro 15 Two charges 4q and q are placed at a distance apart A third charged particle Q is placed at the middle of them If resultant force on q is zero then the value of Q is 2 1 3 20 4 20

1 In a biprism experiment the micrometer readings for zero order and tenth order fringes are 1 25 mm and 2 37mm respectively when light of wavelength 5 90x 105 cm is used Now 4 3 3 Marks a What will be the position of zero order and tenth order fringes if wavelength is changed to 7 50x 10 cm b If a mica sheet of thickness 0 020 mm and 1 59 is introduced to cover one half of the biprism deduce the position of the zero order fringe

If a small amount of antimony is added to germanium crystal 1 it becomes a p type semiconductor 2 the antimony becomes an acceptor atom 3 there will be more free electrons than holes in the semiconductor 4 its resistance is increased SC0137

80 Two identical thin rings each of radius R metre are co axially placed at distance R metre apart If Q and Q coulomb are respectively the charges uniformly spread on the two rings the work done in moving a charge q from the centre of one ring to that of the other is 6 a zero c q 2 Q Q 4TE R d q Q Q 2 1 2 4TE R q Q Q 2 1 2 4 R

1 A hypodermic syringe contains a medicine with the density 1000kg m The barrel of the syringe has a cross sectional area A 2 50 105 m and the needle has a cross sectional area a 1 00 x 108 m In the absence of a force on the plunger the pressure everywhere is 1 00 atm A force F of magnitude 2 00 N acts on the plunger making medicine squirt horizontally from the needle Determine the speed of the medicine as it leaves the needle s tip 00

The wind resource at hub height for a wind turbine with rated power of 5 1 MW at a wind speed 12 m s and cut out wind speed 26 m s is described by a Weibull distribution with a shape factor 2 and a scale factor 6 1 m s Calculate the energy production from generating at rated power during a full year of 8760 hours Give the answer to 1 MWh

A resistor of resistance R 1000 2 is maintained at 17 C and it shunted by 100 H inductor Determine the rms noise voltage across the inductor over a frequency bandwidth of i ii iii 15 9 kHz 159 kHz 1590 kHz Ans 182 x10 volt Ans 9 22 x108 volt Ans 2 34 x10 volt Your answer Typed answers are easier for students to read than handwritten notes

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A 2 mm by 2 mm square probe is immersed in a 3 eV xenon plasma a If the probe collects 1 mA of ion current what is the plasma density Hint the probe has two sides and is considered infinitely thin b What is the floating potential c What is the probe current collected at the plasma potential

straight line depends upon value of 6 n is the unit vector along incident ray n along normal and n is the unit vector along reflected ray then which of the following must be true 1 0 X 2 3 0X 3 x 3 0

The beautiful colors of a blue morpho butterfly are known to be originated from nanoscale structures that function as a natural diffraction grating Suppose the diffraction grating has 7000 lines cm what is the angle of the second order maximum for 633 nm light 47 2 26 3 62 4 20

g a 8 A rocket has a mass of 20000 kg of which 16000 kg is fuel The rocket eng rate of 200 kg s with an exhaust velocity of 3000 m s relative to the rocket the rocket 10 second after blast off Take g 10 m s 1 4 2 10 N 2 6 10 N 3 18 105N 4

12 15 80 51 min 59 secs A particle is projected from infinity with a velocity of The perpendicular distance between the target and initial velocity is b The mass of the particle m experiences repulsive inverse square force Then closes approach d is

5 The table shows the length of a spring under a specific load Load kg 0 1 2 3 4 5 6 Length cm 12 0 12 6 13 8 15 6 18 0 21 0 24 6 a Use finite differences to determine whether this is a quadratic relation

2 Determine the minimum value of P to just lift the block W 500 N where 0 20 as shown The coefficient of static friction at all contact surfaces is Hs 0 30 Neglect the weight of the wedge W

51 A current of 3 A flows through the 2 2 res shown in the circuit The power dissipated in 5 resistor is 1 5 watt 3 2 watt 2922 19 492 ww 592 AIPMT Prelims 20 2 4 watt 4 1 watt

b The convex surface of radius of curvature 300cm of a plano convex lens rests on the concav spherical surface of radius 400cm If Newton s rings are viewed with reflected light wavelength 6x105cm Calculate i the diameter of the 12th dark ring and 13th bright ring ii the difference of squares of the diameters of successive rings

A particle of mass m is kept at the top of a smooth fixed sphere It is given a horizontal velocity v then 1 it will start moving along a circular path if v gR 2 it will start moving along a circular path if v gR 3 it will start moving along a parabolic path if v gR 4 it will start moving along a parabolic path if v gR Gurukripe Career Institute Pvt Ltd Jyeti Nagar Piprali Road Sikar Ph 01572 256688

51 A metal coin of mass 5g and radius 1 cm is fixed to stick AB of negligible mass as shown in the figure The system is initially at rest The constant torque that will make the system rotate about AB at 25 rotations per second in 5s is close to 2019 Main A Ja a 4 0 x 10 6 N m c 16 x 105 N m 1 cm b 20 x 105 N m d 79 x 10 6 N

1 125 Consider the flow of saturated steam at 270 1 kPa that flows through the shell side of a shell and tube heat exchanger while the water flows through 4 tubes of diameter 1 25 cm at a rate of 0 25 kg s through each tube The water enters the tubes of heat exchanger at 20 C and exits at 60 C Due to the heat exchange with the cold fluid steam is condensed on the tubes external surface The convection heat transfer coefficient on the steam side is 1500 W m K while the fouling resis tance for the steam and water may be taken as 0 00015 and 0 0001 m K W respectively Using the NTU method deter mine a effectiveness of the heat exchanger b length of the tube and c rate of steam condensation Saturated steam UU 60 C 20 C Water

It is desired to photograph the image of an object placed at a distance of 3m from the plane mirror The camera which is at a distance of 4 5m from the mirror should be focussed for a distance of a 3m c 6m Camera 917439747061 as5716009 gmail com 0 4 5m b 4 5m d 7 5m 3m

Four thin lenses of powers 2 D 1 D 4 D and 1 D are placed in contact with each other The equivalent power of the combination will be 8 D 3 D min sec 4 D

In a lab you have two centrifuges Centrifuge A rotates with a maximum frequency of 2000 Hz and the sample sits 6 0 cm from the rotation axis Centrifuge B rotates with a maximum frequency of 4000 Hz but the sample sits 3 0 cm from the rotation axis If your sample sediments in 100 minutes when using centrifuge A how long would it take to sediment using centrifuge B 400 minutes 25 minutes 100 minutes 200 minutes 50 minutes

A of mass 4 kg which in turn is place smooth surface coefficient of frictio between blocks is 0 30 Horizontal f Fo 24 N is applied on block A If acceleration of block A and B are a ag respectively then g 10 m s B 2 kg A 4 kg One More Correct Answer s Fo Smooth i

Refractive index of air depends on temperature and pressure Within few metres of height difference near the ground air pressure remains almost uniform but air temperature changes by appreciable amount Suppose under such conditions the refractive index u depends only on the temperature and this dependence has the form a 1 T Here a is a constant value of which at normal pressure is 1 6 K The sun heats up the air above a road and simultaneous random small movements of air make the dry asphalt appear like a puddle This phenomenon is called mirage Suppose that in a thin layer immediately above the road temperature of air is AT 20 K more than temperature To 300 K of the air elsewhere From what minimum horizontal distance x an observer of height h 1 75 m can see a puddle on the road otic T Al

yman wants to put his Arowana fish in a special tank He would like to DIY the tank o be open rectangular shape and should have a volume of 2 85m where m is in meter Compute the least surface area of the glass that Ayman required to DIY the tank

The radius of curvature of a convex mirror of focal length 20 cm will be 20 cm 10 cm 40 cm min se 30 cm

In the figure ABC is the cross section of a right angled prism and BCDE is the cross section of a glass slab The value of 0 so that light incident normally on the face AB does not cross the face BC is given sin 3 5 37 A 0 37 B 0 37 4 C 0 53 D 0 53

O 1 is transmitted by a positive pulse and 0 is transmitted by negative pulse O 1 is transmitted by a positive pulse and 0 is transmitted by zero volts 1 is transmitted by a positive half pulse and 0 is transmitted by negative half pulse 1 is transmitted by a positive half pulse and 0 is transmitted by zero volts

The tangents of a simple curve have bearings of N 20 E and N 80 E respectively The radius of the curve is 200m 1 Compute the external distance of the curve a 43 90m b 30 94m 2 Compute the middle ordinate of the curve b 27 20m a 26 79m c 29 62m d 27 96m 3 Compute the stationing of point A on the curve having a deflection angle of 6 from the PC which is at 1 200 00 a 1 731 b 1 956 c 49 63m c 1 241 89 d 34 90m d 1 158 11

2 a In a bi prism experiment with sodium light 5893 the micrometer reading is 2 32mm When the eye piece is placed at a distance of 100cm from the source If the distance between two virtual sources is 2 cm Find the new reading of the micrometer if the eye piece is moved such that 20 fringes cross the field view 4 4 2 Marks