The rear side of truck is open and box of mass 50kg is placed at 3.2m away from the open end.The coefficient of friction between the box and the surface is 0.2. if the truck starts from rest and moves on a straight road with acceleration 2.1ms-2 the box falls off the truck after a time (g=10ms-2)
(8/√41)s
4s
8s
√8s
When the angle of inclination of an inclined plane is θ, an object slides down with uniform velocity. If the same object is pushed with a initial velocity u on the same inclined plane; it goes up the plane and stops at a certain distance on the plane. Thereafter the body :
slides down the inclined plane and reaches the ground with velocity u.
slides down the inclined plane and reaches the ground with velocity less than u.
slides down the inclined plane and reaches the ground with velocity greater than u.
stays at rest on the inclined plane and will not slide down.
A rod with linear charge density λ is bent in the shape of circular ring.The electric potential at the centre of the circular ring is
2λ/ε0
λ/ε0
λ/2ε0
λ/4ε0
Four resistors A,B,C and D form a Wheatstones bridge. The bridge is balanced when C = 100Ω .If A and B are interchanged, the bridge balances for C= 121Ω.The value of D is
10Ω
100Ω
110Ω
120Ω
Two tuning forks of frequencies 250 and 256 Hz produce beats.If maximum is produced now,thus the minimum time after which minimum is produced at that same place
(1/18)s
(1/24)s
(1/6)s
(1/12)s
Resistances are connected in the two gaps of a meter bridge.The balance point is 20cm from the zero end.When a 15Ω resistor is connected in series with the smaller resistance then the null point shifts to 40cm.the smaller resistance is
80Ω
9Ω
12Ω
When a uniform wire of radius r, is stretched by a 2 kg weight the increase in its length is 2.00 mm. If the radius of the wire is r/2 and other conditions remaining the same, the increase in its length is
2.00 mm
4.00 mm
6.00 mm
8.00 mm
A vessel is filled with an ideal gas at a pressure of 10 atmosphere and temperature 270C. Half of the mass of the gas is removed from the vessel and temperature of the remaining gas is increased to 870C.Then the pressure of the gas in the vessel will be
5 atm
6 atm
7 atm
8 atm
A wire stretches by 0.01 m when it is stretched by a certain force.Another wire of the same material but double the length and double the diameter is stretched by the same force.The elongation is
0.005 m
0.01 m
0.02 m
0.04 m
In the Young's double slit experiment, the intensities at two points P1, and P2 on the screen are respectively I1, and I2. If P1, is located at the centre of a bright fringe and P2 is located at a distance equal to a quarter of fringe width from P1 then I1/I2 is
2
1/2
1/4
1/16
The third overtone produced by a vibrating string 2m long is 1200 Hz. The velocity of propagation of the wave is
1800 m/s
1600 m/s
1400 m/s
1200 m/s
Two parallel rails of a railway track insulated from each other and with the ground are connected to a millivoltmeter. The distance between the rails is one meter. A train is traveling with a velocity of 72 km/h along the track. The reading of the milli-voltmeter (in mV) is (Vertical component of the earth'smagnetic induction is 2 x 10-5 T)
1.44
0.72
0.4
0.2
The temperature of the system decreases in the process of
free expansion
adiabatic expansion
isothermal expansion
isothermal compression
A liquid of mass m and specific heat S is heated to a temperature T. Another liquid of mass mil and specific heat 2 S is heated to temperature 2 T. If these two liquids are mixed, the resultant temperature of the mixture :
2/3 T
8/5T
3/4T
3/2T
A long rigidly supported wire carries a current ia=96A.Directly above it and parallel to it at a distance,another wire of 0.144N weight per metre carrying a current ib=24A,in a direction opposite to that air due to magnetic repulsion,then its distance(in mm) from the lower wire is
1.6
3.2
4.8
9.6
A uniform chain of length L is lying on the horizontal table. If the coefficient of friction between the chain and the table top is 'μ’ what is the maximum length of the chain that can hang over the edge of the table without disturbing the rest of the chain on the table
L / (1+μ )
μL / (1+μ)
L / (1 - μ)
μL / (1-μ)
Thomson coefficient of a conductor is 10μVK. The two ends of it are kept at 500 C and 600 C respectively. Amount of heat absorbed by the conductor when a charge of 10 C flows through it, is:
1000 J
100 J
100 mJ
1 mJ
A north pole of strength πAm, is moved around a circle or radius 10 cm which lies around a straight conductor carrying a current of 10 A. The work done is nearly
4μJ
40μJ
400 μJ
0.4 μJ
A sonometer is set on the floor of a lift.When the lift is at rest,the sonometer wire vibrates with fundamental frequency 256Hz.When the lift goes up with acceleration a=9g/16,the frequency of vibration of the same wire changes to
512Hz
320Hz
256Hz
204Hz
A wire of length 44cm is bent into a circle and a current of 9.8A is passed through it.The intensity of magnetic induction at the centre of the circle is
8.8x10-6T
8.8 x10-5T
8.4 x10-6T
61.5 x10-5T
If the magnitude of the intensity of a magnetic field at a distance x on the axial line and at a distance y on the equatorial line of a given dipole have the same value the ratio x : y is :
1 : √2
√2 : 1
1:2
21/3 :1
When an unknown resistance and a resistance of 4 ? are connected in the left and right gaps of a meterbridge, The balance point is obtained at 50 cm. The shift in the balance point if a 4 ? resistance is now connected in parallel to the resistance in the right gap is
66.7cm
16.7cm
34.6cm
14.6cm
The loss of weight of a solid when immersed in a liquid at 00C is .If α and β are the volume coefficients of the solid and the respectively, then the loss of weight at C is approximately
W0[1+(α-β)t]
W0[1-(α-β)t]
W0[1-(α+β)t]
W0[2-(α+β)t]
With a standard rectangular bar magnet of length (l), breadth (b; b < < l) and magnetic moment M, the time period of the magnet in a vibration magnetometer is 4 s. If the magnet is cut normal to its length into four equal pieces, the time period (in seconds) with one of the pieces is :
16
1
The natural frequency of an I.-C circuit is 1,25,000 cycle/s. Then the capacitor C is replaced by another capacitor with a dielectric medium of dielectric constant K. In this case, the frequency decreases by 25 kHz. The value of K is
3.0
2.1
1.56
1.7
The resistance of a conductor is 1.08Ω.To reduce it to 1Ω,the resistance that must be connected is
0.08Ω in series
13.5 Ω in parallel
0.08 Ω in parallel
13.5Ω in series
Thomson coefficient of a conductor is 10μV/K.The two ends of it are kept at 500C and 600C respectively.Amount of heat absorbed by the conductor when a charge of 10C flows through it is
1000J
100J
A source of sound is approaching a stationary observer with a velocity 1/10th of the velocity of sound in air so that apparent decrease in the wavelength of sound waves is 10cm.If the observer is approaching the same source of sound at rest with a velocity 1/5th of velocity of sound in air,the apparent increase in the frequency of sound is(velocity of sound in air=340m/s)
34Hz
51Hz
68Hz
85Hz
An intrinsic semi conductor has 1018/m3 free electron and is doped with pentavalent impurity of 1024/m3.Then the free electrons density order increases by
4
3
5
6
In a thermo couple the temperature of the cold junction is 150C.If the temperature of inversion is 4850C,the neutral temperature of the thermo couple is
2350C
9850C
9550C
2500C
When a liquid is heated in copper vessel its Coefficient of apparent expansion is 6x10-6/0C.When the same liquid is heated in a steel vessel its coefficient of apparent expansion is 24x10-6/0C If coefficient of linear expansion for copper is 18x10-6/0C the coefficient of linear expansion for steel is
20x10-6/0C
24x10-6/0C
36x10-6/0C
12x10-6/0C
A train approaching a level crossing at a speed of 20m/s sounds a horn of frequency 628Hz when 80m form the crossing.A person is standing at 60m from the level crossing on a road which is perpendicular to the railway track.Then the apparent frequency heard by the person is (velocity of sound in air is 330m/s)
660Hz
680Hz
640Hz
690Hz
The frequency of a tuning fork x is 5% greater than that of a standard fork of frequency K. The frequency of another fork y is 3% less than of K. When x and y are vibrated together 4 beats per second. The frequencies of x and y are
38.5Hz, 48.5Hz
40.5Hz, 42.5Hz
57.5Hz, 47.5Hz
52.5Hz, 48.5Hz
An observer to moving away from a source of sound of frequency 100 Hz at a speed of 33 m/s. If the speed of the sound in air is 330 m/s and the observed frequency is
90 Hz
100 Hz
91Hz
110 Hz
The wavelength of blue light in air is 45000A if the refractive index for blue light is 1.55 in glass what will be the wavelength of blue light in glass(c=3x108m/s)its frequency is
5.4x1014HZ,7000A0
4.5x1014HZ,3500A0
7.5x1014HZ,3000A0
6.7x1014HZ,2903A0
In a chemical reaction, ΔH=150KJ and ΔS=100JK-1 at 300K. ΔG would be
120KJ
330KJ
300KJ
Zero
A body of weight "64N" is pushed with just enough force to start it moving across a horizontal floor and the same force continues to act afterwards, if the coefficients of static and dynamic friction are 0.6 and 0.4 respectively, the acceleration of the body is: (acceleration due to gravity = g)
g/6.4
0.64g
g/32
0.2g
If a is the radius of first Bohr orbit in hydrogen atom, the radius of 3rd orbit is :
3a
9a
27a
81a
When a high resistance R is connected in series with a voltmeter of resistance G, the range of the voltmeter increases 5 times. Then G:R will be
4:1
8:1
1:4
A whistling engine is approaching a stationary observer with a velocity of 110m/s. The velocity of sound is 330m/s. The ratio of frequencies as heard by the observer as the engine approaches and recedes is
2:1
3:6
4:3
The capacity of a parallel plate condenser consisting of two plates each 10 cm square and are separated by a distance of 2mm is (Take air as the medium between the plate):
88.5 x 10-13 F
44.42 x 10-12 F
4.42 x 10-11 F
8.85 x 10-13 F
A quantity of heat Q is supplied to a mono atomic ideal gas which expands at constant pressure. The fraction of heat that goes into work done by the gas is :
2/5
3/5
2/3
The tyre of a motor car contains air at 150C. If the temperature increases to 350C, the approximate percentage increase in pressure is (ignore to expansion of tyre)
7
9
11
13
In an electric motor,wires carrying a current of 5A are placed at right angles to magnetic field of induction 0.8T.If each wire has length of 20cm,then the force acting on each wire
0.8N
0.6N
0.4N
0.2N
If 4 moles of an Ideal monoatomic gas at temperature 400 K is mixed with 2 moles of another ideal monoatomic gas at temperature 700 K, the temperature of the mixture is:
550oC
500oC
550 K
500 K
The pair of physical quantities not having the same dimensional formula is :
acceleration, gravitational field strength
torque, angular momentum
pressure, modulus of elasticity
all of the above
Photoelectric current can be increased by using :
higher frequency radiation
higher intensity radiation
higher work function of metal plates
none of the above
Two cells A and B are connected in the secondary circuit of a potentiometer one at a time and the balancing length are respectively 400 cm and 440 cm. The emf of the cell A is 1.08 volt. The emf of the second cell B in volts is :
1.08
1.188
11.88
12.8
Consider the two following statements A and B,and identify the correct choice given in the answers:A) In photovoltaic cells the photoelectric current produced is not proportional to the Intensity of Incident light (B) In gas filled photo emissive cells, the velocity of photo-electrons depends on the wavelength of the incident radiation
both A and B are true
both A and B are false
A is true but B is false
A is false but B is true
The radiation emitted by a star A is 10,000 times that of the sun. If the surface temperatures of the sun and the star A are 6000 K and 2000 K respectively, the ratio of the radii of the star A and the sun is:
300 : 1
600 : 1
900: 1
1200 : 1
A horizontal beam of vertically polarized light of intensity 43W/m2 is sent through two polarizing sheets. The polarizing direction of the first is 600 to the vertical , and that of the second is horizontal. The intensity of the light transmitted by the pair of sheets is (nearly)
8W/m2
11W/m2
33W/m2
21.5W/m2
The maximum tension a rope can withstand is 60 kg wt The ratio of maximum acceleration with which two boys of masses 20 kg and 30 kg can climb up the rope at the same time is
3:2
An observer is standing 500 m away from a vertical hill. Starting between the observer and the hill, a police van sounding a siren of frequency 1000 Hz moves towards the hill with a uniform speed. If the frequency of the sound heard directly from the siren is 970 Hz, the frequency of the sound heard after reflection from the hill (in Hz) is about, (velocity of sound = 330ms-1):
1042
1032
1022
1012
A steady current is set up in a metallic wire of non-uniform cross-section. Then the drift velocity related the area of cross-section (A) as
Vd is independent of
Vd A2
Vd A
Vd A-1
Two bar magnets A, B are placed one over the other and are allowed to vibrate in a vibration magnetometer. They make 20 oscillations per minute when the similar poles of A and B are on the same side, while they make 15 oscillations per minute when their opposite poles lie on the same side. If MA and MB are the magnetic moments of A and B and if MA > MB, the ratio of MA and MB is
4 : 3
25 : 7
7 :5
25 : 16
The frequency of a stretched uniform wire under tension is in resonance with the fundamental frequency of a closed tube.If the tension in the wire is increased by 8N, it is in resonance with first overtone of the closed tube.The initial tension in the wire is
16N
8N
4N
1N
Under minimum deviation condition in a prism, if a ray is incident at an angle of 300. The angle between the emergent ray and the second refracting surface of the prism is: ( Angle of prism = 600)
00
300
450
600
A condenser of capacity 10μF is charged to a potential of 500V. Its terminals are then connected to those of an uncharged condenser of capacity 40μF. The loss of energy in connecting them together is
1J
2.5J
10J
12J
The coefficient of kinetic friction between a body and the surface of an inclined plane at 450 is 0.5. If g = 9.8 ms-2,the acceleration of the body down the inclined plane, in ms-2is:
4.9/√2
4.9
4.9√2
19.6√2
A wooden block is dropped from the top of a cliff 100m high.Simultaneously a bullet of mass 10g is fired from the foor of the cliff upwards with a velocity of 100 m/s.The bullet and wooden block will meet each other after a time:
10s
0.5s
1s
7s
A body is projected vertically upwards at time t = 0 and it is seen at a height 'H' at time t1 and t2 seconds during its flight. The maximum height attained is : (g is acceleration due to gravity)
g(t2-t1)2 / 8
g(t1+t2)2 / 4
g(t1+t2)2 / 8
g(t2-t1)2 / 4
A bullet of mass 10 g is fired horizontally with a velocity 1000ms-1 from a rifle situated at a height 50 m above the ground. If the bullet reaches the ground with a velocity 500ms-1, the work done against air resistance in the trajectory of the bullet is : (g=10ms-2)
5005J
3755J
3750J
17.5J
A body of mass m is suspended to an ideal spring of force constant k. The expected change in the position of the body due to an additional force F acting vertically downwards is
3F/2k
2F/k
5F/2k
4F/k
The work function of the nickel is 5 eV. When a light of wavelength 2000 Ao falls on it, it emits photo electrons in the circuit. Then the potential difference necessary to stop the fastest electrons emitted is (given h = 6.67 x 10-34 J-s)
1.0 V
1.75 V
1.25 V
0.75 V
A condenser of 20μF is charged to a certain voltage and then discharged through a 4x106Ω resistor.The time taken for the condenser to lose 63% of its charge is
50s
80s
5s
A wire of length l having tension T and radius r vibrates with fundamental frequency f.Another wire of the same metal with length 2l having tension 2T and radius 2r will vibrate with fundamental frequency
f
2f
3f/2
in a half wave rectifier output is taken across a 90 ohm load resistor. If the resistance of diode in forward biased condition is 10 ohm, the efficiency o rectification of ac power into dc power is
40.6%
81.2%
73.08%
36.54%
A given mass of a gas is compressed isothermally until its pressure is doubled. It is then allowed to expand adiabatically until its original volume is restored and its pressure is then found to be 0.75 of its initial pressure.The ratio of the specific heats of the gas is approximately
1.20
1.41
1.67
1.83
If a body is in equilibrium under a set of non-collinear forces, the minimum number of forces has to be
four
three
two
five
If the angle of a prism is 600 and angle of minimum deviations is 400, then the angle of refraction in the prism will be
500
200
A sonometre wire vibrating in 4 segments is in unison with the tuning fork. Keeping the same length, if the tension made 4 times the tuning fork can still be in resonance with the wire provided the wire now vibrates in
4 segments
6 segments
3 segments
2 segments
A particle of mass 4 m explodes into three pieces of masses m, m and 2 m. The equal masses move along X- and Y-axes with velocities 4 ms-1 and 6 ms-1 respectively. The magnitude of the velocity of the heavier mass is
√17 ms-1
2√13 ms-1
√13 ms-1
√13 / 2 ms-1
Keeping the banking angle sam,to increase the maximum speed with which a vehicle can travel on a curved road by 10 percent the radius of curvature of the road has to be changed from 20m to :
6m
18m
24.2m
30.5m
The centre of mass of three particles of masses 1 kg, 2 kg and 3 kg is at (2, 2, 2).The position of the fourth mass of 4 kg to be placed in the system as that the new centre of mass is at (0, 0, 0) is :
(-3,-3,-3)
(-3,3,-3)
(2,3,-3)
(2,-2,-3)
The fundamental frequency of a sonometer wire is 200 Hz when a body whose relative density 4 is suspended at the end of wire.The fundamental frequency of the same wire when the suspended body is made to immerse in water is
100√2Hz
100√3 Hz
50√2 Hz
50√3 Hz
Two identical sringed instruments have frequency 100Hz. If tension in one of them is increased by 4% and they are sounded together, then number of beats in one second is
The frequency of a tuning fork A is 2% greater than that of standard fork K.The frequency of another tuning fork B is 3% less than K.When A and B are vibrated together 6 beats per second are heard per second. The frequencies of A and B are
122.4Hz,116.4Hz
132.4Hz,116.4Hz
142.4Hz,116.4Hz
152.4Hz,116.4Hz
A large tank filled with water to a height h is to be emptied through a small hole at the bottom The ratio of times taken for the level of water to fall from h to h/2 and h/2 to zero is
√2
1/√2
√2-1
1/(√2-1)
A bar-magnet of moment of inertia 49 x 10-2 kg-m2 vibrates in a magnetic field of induction 0.5 x10-4 T. The time period of vibration is 8.8 s. The magnetic moment of the bar magnet is
350 A-m2
490 A-m2
3300 A-m2
5000 A-m2
A horizontal pipe of non-uniform cross-section allows water to flow through it with a velocity 1 ms-1 when pressure is 50 kPa at a point. If the velocity of flow has to be 2 ms-1 at some other point, the pressure at that point should be
50 kPa
100 kPa
48.5 kPa
24.25 kPa
A rectangular class room of volume 20×15×10 m3 has a surface whose average absorption coefficient is 0.035. When a material of area 1500m2 is brought into the room, the reverberation time falls to 2.5 seconds. The absorption coefficient of the material is nearly
0.04
0.12
0.28
0.36
A motor car of mass 300 kg is moving with a velocity of 25 m/s, by applying brakes the car was brought to rest in a distance of 15 metres. The force of retardation in newton is :
2500
4500
6250
7500
A current is passed through two coils connected in series. The potential difference across the first coil is 3 volts and that of the second coil 4.5 volts. If the first coil has resistance of 2 ohm, the resistance of the second coil is:
3Ω
5Ω
7Ω
7N14+2He4→X+1H1 then ‘X’ is
9F18
10Ne18
8O17
8C15
Dispersive power depends on the following :
material of the prism
shape of the prism
size of the prism
size, shape and material of the prism
If c is velocity of light in fre space,the time taken by the light to travel a distance x in a medium of refractive index μ is given by:
μxc
μx/c
μc/x
x/μ
At least how many thermal neutrons should be available to start a fission reaction
Assertion (A): Propagation of light through an optical fibre is due to total internal reflection taking place at the core-clad interface.Reason (R): Refractive index of the material of the core of the optical fibre is greater than that of air.
both (A) and (R) are true and (R) is the correct explanation of (A)
both (A) and (R) are true but (R) is not the correct explanation of (A)
(A) is true but (R) is false
(A) is false but (R) is true
In an n-type semiconductor, the Fermi energy level lies
in the forbidden energy gap nearer to the conduction band
in the forbidden energy gap nearer to the valence band
in the middle of forbidden energy gap
outside the forbidden energy gap
The rate constant of the reaction at temperature 200K is 10 times than the rate constant at 400K.The activation energy of the reaction is
1842.4R
921.2R
460.6R
230.3R
The magnetic induction and the intensity of magnetic field inside an iron core of an electromagnet are 1 Wb m-2 and 150 Am-1 respectively. The relative permeability of iron is :(μ0=4π x 10-7 henry/m)
106/4π
106/6π
105/4π
103/6π
Two lenses of focal lengths +10cm, and -15cm when put in contact behave like a convex lens .They will have zero longitudinal chromatic aberration if their dispersive powers are in the ratio
+3/2
+2/3
-3/2
-1/2
The effect due to uniform magnetic field on a freely suspended magnetic needle is as follows :
both torque and net force are present
torque is present but no net force
both torque and net force are absent
net force is present but not torque
The dark lines in the solar spectrum are due to:
Absorption of certain wavelengths by elements present in the outer layer
Absence of certain elements in the sun
Black body radiation from the sun
Scattering of light
The R.L of water is 4/3.If ray travels 24cm in air in a given time t,the distance traveled by light in water in the same time t is
12cm
18cm
24cm
32cm
A liquid of mass ‘m’ and specific heat C is heated to a temperature 2T.Anither liquid of mass m/2 and specific heat 2C is heated to a a temperature T.If these two liquids are mixed,the resulting temperature of mixture is
(2/3)T
(8/5)T
(3/5)T
(3/2)T
A liquid does not wet the solid surface if the angle of contact is
zero
equal to 450
equal to 900
greater than 900
Two point charges -q and +q are located at points (0, 0, -a) and (0, 0, a) respectively. The electric potential at a point (0, 0, z), where z > a
qα/ 4πεoz2
q/ 4πεoα
2qα/ 4πεo (z2 - a2 )
2qα/ 4πεo (z2 + a2 )
Two positive charges q1=4x10-6C and q2=9x10-6C are placed 10cm apart in air. The position of a third charge to be placed between them, such that there will be no resultant force on it is
6cm from q1
3cm from q1
4cm from q1
7cm from q1
The difference between heats of reaction at constant pressure and at constant volume for the reaction 2C6H6(l)+15O2(g) → 12CO2(g)+6H2O(l) at 250C in KJ is
+7.43
-3.72
+3.72
-7.43