Physics Questions and Answers October 12, 2022

A radio transmitter operates at a freqency 880 kHz and a power of 10 kW. The number of photons emitted per second is (a) 1.72 101 (c) 1.327 x 107 (b) 1.327 1025 (d) 1.327 x 105

A ball of mass 2kg is thrown up with a speed of 10m/s. find the kinetic energy of the ball at the time of throwing. Also find the potential energy of the ball at the highest point? 40 J 100 J 400 J 10 J None of these

A bus travels at a speed of 50 km/h to go from its origin of its destination at a distance of 300 km and travels at a speed of 60 km/h to return to the origin. What is the average speed of the bus? 55.55 km/h 55 km/h 54.55 km/h 54 km/h None of these

A stone is dropped from the top of a tower which is 19.6 m high. What will be its velocity just before striking the ground? Take g = 9.8 m/s 2 . 9.8 m/s 19.6 m/s 39.2 m/s 13.86 m/s None of these

The odometer, of a bus reads 1400 km at the start of a trip and 1900 km at the end of the trip.

Two particles A and B are connected by a rigid rod AB. The rod slides along perpendicular rails as shown here. The velocity of A to the left is 10 ms. What is the velocity of B when angle a 60 B (a) 5.8 ms (c) 10 ms (b) 9.8 ms (d) 17.3 ms

The electric intensity due to a dipole of length 10 cm and having a charge of 500 C, at a point on the axis at a distance 20 cm from one of the charges in air, is (a) 6.25 x 10 NC (c) 13.1 x 10 NC (b) 9.28 x 10 NC (d) 20.5 x 10 NC

If the nuclear radius of Al is 3.6 Fermi, the approximate nuclear radius of 64Cu in Fermi is (a) 2.4 (c) 4.8 (b) 1.2 (d) 3.6

A small sphere is attached to a cord and rotates in a vertical circle about a point O. If the average speed of the sphere is increased, the cord is most likely to break at the orientation when the mass is at (a) bottom point B (b) the point C (c) the point D (d) top point A D

Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are K, and K. The thermal conductivity of the composite rod will be 2017 (a) 3(KK) 2 (b) K, K (c) 2 (K, K) K K (d) 2 B d

An artificial satellite is moving in a circular orbit of radius 41225km. Calculate its speed if it takes 25 hours to revolve around the earth.

Four point charges Q, q, 2q and 20 are placed, one at each corner of the square. The relation between Q and q for which the potential at the centre of the square is zero is (a) Qq (b) Q (d) Q (c) Q q q q

A coil has resistance 30 ohm and inductive reactance 20 ohm at 50 Hz frequency. If an ac source, of 200 volt, 100 Hz, is connected across the coil, the current in the coil will be (a) 4.0 A 20 (c) A 13 (b) 8.0 A (d) 2.0 A

Two rods of thermal conductivities K, and K, crosssections A, and A, and specific heats S, and S, are of equal lengths. The temperatures of two ends of each rod are T, and T. The rate of flow of heat at the steady state will be equal if K K (a) A S A S (b) KA KA (c) KS KS (d) A S AS

Nisha walks on a 100m long path. She covers 160m in one minute by walking from one end to the other and back along the same straight path. Find the average speed.

A sample has 4 x 106 radioactive nuclei of half life 10 days. The number of atoms decaying in 30 days is (a) 3.9 x 106 (c) 106 (b) 5 x 105 (d) 3.5 106

An engine has an efficiency of 16. When the temperature of sink is reduced by 62C, its efficiency is doubled. Temperature of the source is (a) 37C (c) 99C (b) 62C (d) 124C

Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volt and the average resistance per km is 0.5 . The power loss in the wires is (a) 19.2 W (c) 19.2 J (b) 19.2 kW (d) 12.2 kW

Two particles are oscillating along two close parallel straight lines side by side, with the same frequency and amplitudes. They pass each other, moving in opposite directions when their displacement is half of the amplitude. The mean positions of the two particles lie on a straight line perpendicular to the paths of the two particles. The phase

A particle executes linear simple harmonic motion with an amplitude of 3 cm. When the particle is at 2 cm from the mean position, the magnitude of its velocity is equal to that of its acceleration. Then its time period in seconds is 5 (a) KEKKE

A paper, with two marks having separation d, is held normal to the line of sight of an observer at a distance of 50m. The diameter of the eyelens of the observer is 2 mm. Which of the following is the least value of d, so that the marks can be seen as separate The mean wavelength of visible light may be taken as 5000 (a) 1.25 m (c) 1.25 cm (b)

A weightless ladder 20 ft long rests against a trictionless wall at an angle of 60 from the horizontal. A 150 pound man is 4 ft from the top of the ladder. A horizontal force is needed to keep it from slipping. Choose the correct magnitude of the force from the following (a) 175 lb (c) 120 lb (b) 100 lb (d) 69.2 lb

Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2 I, respectively. The resultant magnetic field induction at the centre will be (a) (b) 2R Hol (c) 5,I 2R 3l (d) Hol R

A photoelectric surface is illuminated successively by monochromatic light of wavelength and 2. If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface of the material is (h Plancks constant, c speed of light) 2015 RS hc (a) 2hc (b) hc hc 2

A car moves from X to Y with a uniform speed v and returns to Y with a uniform speed v. The average speed for this round trip is (a) VuVd Vd Vu (b) (c) (d) VdVu VuVd 2 2vdVu VdVu

The moment of inertia of a body about a given axis is 1.2 kg m. Initially, the body is at rest. In order to produce a rotational kinetic energy of 1500 joule, an angular acceleration of 25 radiansec must be applied about that axis for a duration of (a) 4 seconds (c) 8 seconds (b) 2 seconds (d) 10 seconds

Each of the two strings of length 51.6 cm and 49.1 cm are tensioned separately by 20 N force. Mass per unit length of both the strings is same and equal to 1 gm. When both the strings vibrate simultaneously the number of beats is (a) 7 (c) 3 (b) 8 (d) 5

A bar magnet of length 1 and magnetic dipole moment M is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be MTENIEMINM (a) M M (c) (d) M 60

The momentum of a photon of an electromagnetic radiation is 3.3 10 kgms. What is the frequency of the associated waves h 6.6 104 Js c 3 10 ms ) 13 (a) 1.5 10 Hz (c) 6.0 10 Hz (b) 7.5 102Hz (d) 3.0 10 Hz

The radius of a planet is twice the radius of earth. Both have almost equal average massdensities. If V, and V are escape velocities of the planet and the earth, respectively, then NEET Kar. 2013 (a) V 1.5V, E (b) V 1.5V (c) V2V (d) V 3V E P

The driver of a car travelling with speed 30 msec towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 ms, the frequency of reflected sound as heard by driver is (a) 555.5 Hz (c) 500 Hz (b) 720 Hz (d) 550 Hz

A long solenoid of diameter 0.1 m has 2 10 turns per meter. At the centre of the solenoid, a coil of 100 turns and radius 0.01 m is placed with its axis coinciding with the solenoid axis. The current in the solenoid reduces at a constant rate to OA from 4 A in 0.05 s. If the resistance of the coil is 107 2. the total charge flowing through the

The position vector of a particle is r (a cos wt)i (a sin wt). The velocity of the particle is (a) directed towards the origin (b) directed away from the origin (c) parallel to the position vector (d) perpendicular to the position vector

A boat which has a speed of 5 kmhr in still water crosses a river of width 1 km along the shortest possible path in 15 minutes. The velocity of the river water in kmhr is (a) 3 (c) 21 (b) 4 (d) 1

Four electric charges q, q, q and q are placed at the corners of a square of side 2L (see figure). The electric potential at point A, midway between the two charges q and q, is 9 1 2q 4 L 1 2q 4E L 1 2q 4E L (a) (b) (c) (d) zero q (1 5) (1 5) (1 ) 9

Two blocks A and B of masses 3m and m respectively are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in figure. The magnitudes of acceleration of A and B immediately after the string is cut, are respectively bol (a) g (b) g, bol bo (d) g 6.0 5000l moolm A 3m Bm

A black body has maximum wavelength at temperature 2000 K. Its corresponding wavelength at temperature 3000 K will be (a) am (b) m m (c) am (d) m

A force acts on a 30 gm particle in such a way that the position of the particle as a function of time is given by x 3t 4t t, where x is in metres and t is in seconds. The work done during the first 4 seconds is (a) 576 mJ (c) 490 mJ (b) 450 mJ (d) 530 mJ

A current of 2A flows through a 20 resistor when connected across a battery. The same battery supplies a current of 0.5 A when connected across a 90 resistor. The internal resistance of the battery is (a) 0.5 (c) 14 (b) 13 (d) 1

N molecules each of mass m of a gas A and 2N molecules each of mass 2m of gas B are contained in the same vessel which is maintained at temperature T. The mean square velocity of molecules of B type is v and the mean square rectangular component of the velocity of A type is denoted by o. Then 02 (a) 2 (c) 13 (b) 1 (d) 23

Ten identical cells connected in series are needed to heat a wire of length one meter and radius r by 10C in time t. How many cells will be required to heat the wire of length two meter of the same radius by the same temperature in time t (a) 10 (c) 30 (b) 20 (d) 40

A metal ball of mass 2 kg moving with a velocity of 36 kmh has a head on collision with a stationary ball of mass 3 kg. If after the collision, the two balls move together, the loss in kinetic energy due to collision is (a) 140 J (c) 60 J (b) 100 J (d) 40 J

An automobile moves on a road with a speed of 54 km h. The radius of its wheels is 0.45 m and the moment of inertia of the wheel about its axis of rotation is 3 kg m. If the vehicle is brought to rest in 15s, the magnitude of average torque transmitted by its brakes to the wheel is,2 (a) 8.58 kg m s (c) 2.86 kg m s 2 (b) 10.86 kg m s (d) 6.66 kg m

A spring of force constant k is cut into lengths of ratio 1 2 3. They are connected in series and the new force constant is k. Then they are connected in parallel and force constant is k. Then k k is (a) 19 (c) 114 (b) 111 (d) 16

If a car at rest accelerates uniformly to a speed of 144 kmh in 20 s, it covers a distance of (a) 2880 m (c) 400 m (b) 1440 m (d) 20 m

(a) F (b)F (c) F (d) 2F B,A current carrying loop in the form of a right angle isosceles triangle ABC is placed in a uniform magnetic field acting along AB. If the magnetic force on the arm BC is F, what is the force on the arm AC

A string of 7 m length has a mass of 0.035 kg. If tension in the string is 60.5 N, then speed of a wave on the string is (a) 77 ms (c) 110 ms (b) 102 ms (d) 165 ms

A car is moving towards a high cliff. The car driver sounds a horn of frequency f. The reflected sound heard by the driver has frequency 2f. If v be the velocity of sound, then the velocity of the car, in the same velocity units, will be (a) v 2 (c) v 3 (b) v 2 (d) v 4

A bullet is fired from a gun with a speed of 1000 ms in order to hit a target 100 m away. At what height above the target should the gun be aimed (The resistance of air is negligible and g 10 ms) (b) 10 cm (a) 5 cm (c) 15 cm (d) 20 cm

The bulk modulus of a spherical object is B. If it is subjected to uniform pressure p, the fractional decrease in radius is (a) BBp38pB

A semicircular arc of radius a is charged uniformly and the charge per unit length is . The electric field at the centre of this arc is (a) (b) (c) (d) 2 2a 4 2 2

If the nucleus 13Al has nuclear radius of about 3.6 fm, then 25Te would have its radius approximately as (a) 9.6 fm (c) 4.8 fm 32 (b) 12.0 fm (d) 6.0 fm.

A black body is at a temperature of 5760 K. The energy of radiation emitted by the body at wavelength 250 nm is U, at wavelength 500 nm is U, and that at 1000 nm is U. Wiens constant, b 2.88 10 nmK. Which of the following is correct (a) U 0 (c) U U (b) U0 (d) U U

Three concentric spherical shells have radii a, b and c (a b c) and have surface charge densitieso, o and respectively. If V, V and V denotes the potentials of the three shells, then for c a b, we have (a) V V C B (b) V V V V A (c) VV V (d) Vc V V B

A cylindrical rod having temperature T, and T, at its end. The rate of flow of heat is Q, calsec. If all the linear dimensions are doubled keeping temperature constant, then the rate of flow of heat Q will be (a) 4Q (c) Q4 (b) 2Q (d) Q2

If a negligibly small current is passed through a wire of length 15 m and of resistance 502 having uniform crosssection of 6 107 m, then coefficient of resistivity of material, is Qm Qm (a) 1 x 10 (c) 3 x 10 (b) 2 10 Qm (d) 4 x 10 Qm

A beam of monochromatic light is refracted from vacuum into a medium of refractive index 1.5, the wavelength of refracted light will be (a) dependent on intensity of refracted light (b) same (c) smaller (d) larger

A potentiometer wire has length 4 m and resistance 802. The resistance that must be connected in series with the wire and an accumulator of e.m.f. 2V, so as to get a potential gradient 1 mV per cm on the wire is (a) 40 (c) 48 (b) 44 (2 (d) 32 Q2

A npn transistor is connected in common emitter configuration in a given amplifier. A load resistance of 800 2 is connected in the collector circuit and the voltage drop across it is 0.8 V. If the current amplification factor is 0.96 and the input resistance of the circuit is 19202, the voltage gain and the power gain of the amplifier will

Point masses m, and m, are placed at the opposite ends of a rigid rod of length L, and negligible mass. The rod is to be set rotating about an axis perpendicular to it. The position of point P on this rod through which the axis should pass so that the work required to set the rod rotating with angular velocity oo, is minimum, is given by (a) x

The angular momentum of a body with mass (m), of inertia (I) and angular velocity (o) radsec is moment equal to (a) Io (b) Io

The height at which the weight of a body becomes 116th, its weight on the surface of earth (radius R), is (a) 5R (c) 3R (b) 15R (d) 4R

A magnetic needle suspended parallel to a magnetic field requires 3 J of work to turn it through 60. The torque needed to maintain the needle in this position will be (a) 23)(b) 3J (c) 3J (d) J

A geostationary satellite is orbiting the earth at a height of 5R above that surface of the earth, R being the radius of the earth. The time period of another satellite in hours at a height of 2R from the surface of the earth is (a) 5 (b) 10 (c) 62 6 (d)

A thin semicircular conducting ring (PQR) of radius r is falling with its plane vertical in a horizontal magnetic field B, as shown in figure. The potential difference developed across the ring when its speed is v, is XX X XBX X XX XXX X X X R X X X X X X X (a) Zero (b) Bvr 2 and P is at higher potnetial (c) rv and (d) 2rBv and R is at higher

When an elastic material with Youngs modulus Y is subjected to stretching stress S, elastic energy stored per unit volume of the material is (b) SY2 (a) YS2 (c) S 2Y (d) S2Y

A hollow insulated conduction sphere is given a positive charge of 10 C. What will be the electric field at the centre of the sphere if its radius is 2 metres (a) zero 2 (c) 20 Cm (b) 5 Cm (d) 8 Cm

Consider the following ideal transformer circuit below. V, 11060 V rms. (a) Find I, and I (b) Find V, and V (c) Find the average power dissipated in the 1202 resistor and j3 inductor. (d) Find the total complex power supplied by the source. I Vs 202 ww 2 1 1292 j3N

The radius of germanium (Ge) nuclide is measured to be twice the radius of Be. The number of nucleons in Ge are (a) 74 (c) 72 (b) 75 (d) 73

Find the value of the currents I1, I2 and I3 flowing clockwise in the first, second and third mesh respectively. 5V 1 ohm a) 1.54A, 0.189A, 1.195A b) 2.34A, 3.53A, 2.23A c) 4.33A, 0.55A, 6.02A d)1.18A, 1.17A, 1.16A w 3 ohm 2 ohm 5 ohm 4 ohm 10V

Consider the following system whereGZAS(z) is the combination of ZOH, analog system 5(s40) G(s) and the sampler with sampling time of 0.01s. Suppose C(z) K. (s1)(s10) (s20) R(z) E(z) C(z) U(z) GZAS(z) Y(z) (a) Use MATLAB to find GZAS(z). (b) Analyze the stability of the digital system and find the stable range of K with Jury test. (c) Use

Consider a car moving along a straight horizontal road with a speed of 72 kmh. If the coefficient of static friction between the tyres and the road is 0.5, the shortest distance in which the car can be stopped is (taking g 10 ms) (a) 30 m (c) 72 m (b) 40 m (d) 20 m

If a wire of resistance R is melted and recasted to half of its length, then the new resistance of the wire will be (a) R4 (c) R (b) R2 (d) 2R

In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular path of radius R using a magnetic field B. If,V and B are kept constant, the ratio (charge on the ion) will mass of the ion be proportional to (a) 1R (c) R 2 (b) R (d) 1R

A car moves a distance of 200 m. It covers the first half of the distance at speed 40 kmh and the second half of distance at speed v. The average speed is 48 kmh. Find the value of v (a) 56 kmh (c) 50 kmh (b) 60 kmh (d) 48 kmh

The speed of a wave in a medium is 760 ms. If 3600 waves are passing through a point in the medium in 2 min, then their wavelength is (a) 13.8 m (c) 41.5 m (b) 25.3 m (d) 57.2 m

A closely wound solenoid of 2000 turns and area of crosssection 1.5 x 10 mcarries a current of 2.0 A. It suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field 5 102 tesla making an angle of 30 with the axis of the solenoid. The torque on the solenoid will be (a) 3 10 Nm

A roller coaster is designed such that riders experience weightlesness as they go round the top of a hill whose radius of curvature is 20 m. The speed of the car at the top of the hill is between (a) 14 ms and 15 ms (c) 16 ms and 17 ms (b) 15 ms and 16 ms (d) 13 ms and 14 ms

A ball is thrown vertically upward with a speed of 15 m/s. Determine the time of flight when it returns to its original position.

A ball is thrown vertically upward with a speed of 15 ms. Determine the time of flight when it returns to its original position.

If v = (5s) m/s, where s is in meters, determine a at s = 1 m.

If v = (4t + 5) m/s, where t is in seconds, determine a when t = 2 s.

d) If a = 2 m/s 2 , determine v when t = 2 s if v = 0 when t = 0. e) If a = 2 m/s 2 , determine v at s = 4 m if v = 3 m/s at s = 0.

f) If a = (s) m/s 2 , where s is in meters, determine v when s = 5 m if v = 0 at s = 4 m. g) If a = 4 m/s 2 , determine s when t = 3 s if v = 2 m/s, and s = 2 m when t = 0.

h) If a = (8t 2) m/s 2 , determine v when t = 1 s if v = 0 at t = 0. i) If s = (3t 2 + 2) m, determine v when t = 2 s.

a) If s = (2t 3 ) m, where t is in seconds, determine v when t = 2 s.

Initially, the car travels along a straight road with a speed of 35 m/s. If the brakes are applied and the speed of the car is reduced to 10 m/s in 15 s, determine the constant deceleration of the car.

A rocker climber climbs 63m to the top of a cliff. If the rock climber has a mass of 85kg what is the potential energy of the climber? 5240 joules 52479 joules 5249 joules 5247 joules None of these

A passenger standing in a bus is thrown outward when the bus takes a sudden turn. This happens due to outward pull on him inertia of motion change in momentum change in acceleration None of these

Convert 104F into Degree Celsius. 40C 30C 23C 50C None of these

A block of metal has dimension 4cm,5cm and 25 cm and has a mass of 1.28kg find the density of the block? 2560 (kg/m 3 ) 3452 (kg/m 3 ) 5600 (kg/m 3 ) 1200 (kg/m 3 ) None of these

A piece of wood of mass 160 g and volume of 200 cm 3 find the density of wood in cgs system? 0.8 (g/cm 3 ) 1 (g/cm 3 ) 2 (g/cm 3 ) 4 (g/cm 3 ) None of these

A commonemitter amplifier is shown below. The DC bias gives Ic 0.2 mA (you dont need to calculate the DC bias.) The BJT has 100, C 20 pF and C 2 pF, and the load has CL 10 pF. You can ignore ro and rx in this problem. Assume the coupling and bypass capacitors are large. 92 (10) a) Calculate f. You can find the OCTCs, or use the dominant pole

A worker is pulling a block of mass m up a slope with the angle 8. The pulling force is applied parallel to the slope. The friction coefficients are and us. What pulling force has to be applied to set the block in motion What pulling force is needed to stationary pull the block uphill Calculate the forces for m 30 kg, 0 10, friction wood on

A worker is pulling a block at the angle 8 to the horizontal without acceleration. The mass of the block is m, the coefficient of dry friction is u. What is the value of the force F the worker is applying What is the optimal value of 0 FN mg 0 F

A massless cord goes over a massless block, and the masses m and m are suspended at the ends of the cord. Find the acceleration of the masses and the tension of the cord. T m, mig T m mg

A car is going over a hilltop with the curvature radius R at speed v. Suddenly the driver sees an obstacle behind the hilltop and needs to brake. What is the maximal deceleration if the static friction coefficient is mg fr N

A worker is lifting a heavy block of the mass M with the help of the lever. The far end of the lever is put on the solid floor, and the other end is slowly lifted by the worker. The length of the lever is L. The heavy block is lying on the lever at the distance x from the far end. What force does the worker apply Prove that the total work by all

Find the position of the CM of a system of three masses m 1 kg at r (1,1,1) m, m 2 kg at r (2, 2,2) m, and m3 3 kg at r3 (3,3,3) m.

In the recoil of an object into two parts with masses m and m, the energy AE is released. Find the velocities of the parts 1 and 2.

Derive a general formula for the energy lost in the inelastic collision. Calculate the energy lost and the fraction of the energy lost in the collision of the mass m 1 kg moving with the speed v 2 ms and the mass m 2 kg moving with the speed v2i 1 ms, if in the initial state the masses are moving perpendicularly to each other (the angle