Physics Questions

Example 2 10 a A 900 pF capacitor is charged Fig 2 31 a How much electrostatic energy is stored by the capacitor b The capacitor is disconnected from the battery and connected to another 900 pF capacitor Fig 2 31 b What is the electrostatic energy stored by the system 9 9 D Qx C 100 V TTTTT a N 0 IN O C LIL 2

straight line A particle is resting over a smooth horizontal floor At t 0 a horizontal force starts acting on t Magnitude of the force increases with time according to law F at where a is a positive constant and t is time For the figure shown which of the following statements is are incorrect a xt D 1 Curve 1 shows acceleration against time 3 Curve 2 shows velocity against acceleration 4 none of these dy fat dt 2 Curve 2 shows velocity against time Sav faxtd v xt 2 v kt lvplocity i i k What should be its acceleration so that it can

Magnetic field at point P due to both infinite long current carrying wires is 2 540 6T 5A 5m 2 5A P 2 5m

3 Three particles are projected upward with initial speeds 10m s 20m s and 30 m s The displacements covered by them in their last second of motion are x x and x then 1 4 9 X X 1 x x x 1 2 3 2 3 3 x x x 1 5 7 122 4 None of these 123 2 x x

A man is sitting inside a moving train and observes the objects outside of the train Then choose the single correct choice from the following statements all stationary objects outside the train will move with same velocity in opposite direction of the train with respect to the man 2 stationary objects near the train will move with greater velocity object far from train will move with lesser velocity with respect to the man angular velocity is diff velocity is same 3 large objects like moon or mountains will move with same velocity as that of the train 4 all of these

A wooden block and a metal coin are connected by a string as shown in figure Both have same volume and both are placed in a beaker of water Now the beaker is given acceleration towards right then the string will tilt towards 1 Right 2 No where 3 Left 4 Either right or left

which of the coins will revolve with the 38 You may have seen in a circus a motorcyclist driving in vertical loops inside a death well a hollow spherical chamber with holes so the spectators can watch from outside Explain clearly why the motorcyclist does not drop down when he is at the uppermost point with no support from below What is the minimum speed required at the uppermost position to perform a vertical loop if the radius of the chamber is 25 m

Example 5 6 Two cylinders P and Q rest in a channel as shown in Fig 5 13 B 60 Q P 180 mm D Fig 5 13 The cylinder P has diameter of 100 mm and weighs 200 N whereas the cylinder Q has diameter of 180 mm and weighs 500 N This point will be discussed in more details in the chapter of Principles of Friction

Example 5 15 On a mine site a rock is exploded On explosion rock breaks into three parts Two parts go off at right angles to each other These two are 1 kg first part moving with a velocity of 12 ms and 2 kg second part moving with a velocity of 1 8 ms If the third part flies off with a velocity 4 ms what 11

Velocity v of a particle depends upon the time t according to the equation v a bt C The dimension of bc will be 1 LT 1 3 L T 2 2 LT 2 4 L T 1 d t

Answer the following questions in brief 1 Why do we need food 2 What is the difference between energy provided by carbohydrates and fats How does it help to include sufficient roughage in the diet What makes a balanced diet 3 4 5 How is freezing different than the drying in preserving food

Magnetic field strength at the centre of regular pentagon made of a conducting wire of uniform cross section area as shown in figure is 5 i 4 72 2 2 sin B 0 apel C Not zero if current i leaves D point instead of E D Zero even if the current i leaves point D instead of point E a 72 Eyi

4 6 4 7 Velocity of a stone projected 2 second before it reaches the maximum height makes angle 53 with the horizontal then the velocity at highest point will be 1 20 m s 2 15 m s 3 25 m s 4 80 3 m s A stone projected at angle 0 with horizontal from the roof of a tal building falls on the ground after three

In the figure shown the blocks A C are pulled down with constant velocities u Acceleration of block B is GF V A tan 0 sec 0 b C 1 2 b sec 0 tan 0 B 2 u b tan 0 DXzero A b 010 B b C

6 12 Figure shows a 5 kg ladder hanging from a string that is connected with a ceiling and is having a spring balance connected in between A boy of mass 25 kg is climbing up the ladder at acceleration 1 m s Assuming the spring balance and the string to be massless and the spring to show a constant reading the reading of the spring balance is Take g 10 m s 1 30 kg 2 32 5 kg 3 35 kg 4 37 5 kg

A box of dimensions 1 5 mx 0 75 mx 0 75 m and mass 250 kg rests on a truck with the smaller face down Assuming that the friction is strong enough so that the box does not slip what is the maximum acceleration the truck can have without the box tipping over

a Like there are landforms on land ocean floor also has submerged landforms because i There is land under water ii There are volcanoes under water iii Land is continuous and there is water in deeper parts Though land is continuous its level is not the same everywhere like

Two identical block each of mass M 9 kg are placed on a rough horizontal surface of frictional coefficient 0 1 The two blocks are joined by a light spring and block B is in contact with a vertical fixed wall as shown in figure A bullet of mass m 1 kg and vo 10 m s hits block A and gets embedded in it a Find the maximum compression of spring 0 m olink Mmmm b Find the minimum value of vo for which block B will just start moving left wards Spring constant 240 N m g 10 m s

A battery of 20 cells each having e m f 1 8 V and internal resistance 0 1 2 is charged by 220 volts and the charging current is 15 A Calculate the resistance to be put in the circuit

9 In a comman base connection a certain transistor has an emitter current of 10mA and collector current of 9 8 mA Calculate the value of the base current

Electric potential in an electric field is given as V K r K being constant if position vector r 21 33 6k then electric field will be 21 31 6k K 343 61 2j 3k K 343 1 3 21 3j 6k K 243 31 2j 6k K 243 2 4

6 6 A bob is hanging over a pulley inside a car through a string The second end of the string is in the hand of a person standing in the car The car is moving with constant acceleration a directed horizontally as shown in figure Other end of the string is pulled with constant acceleration a relative to car vertically The tension in the string is equal to 1 mg cos 0 sin 8 ma 3 m g a ma m car a 2 2 m g a ma 4 m g a lock of mass M as shown

Speed of water in a river is 4 km h and man can swim at 5 km h Minimum time taken by the man to cross the river of width 200 m is 1 t h 2 h 25 1 15 h

Find the time taken by the particle in going from x 0 to x 2 x Asinot A 2 A sin ot T sin sin 6 TU 2 11 6 T t 2 t t T 12 where A is the amplitude

A block is placed on a rough horizontal plane A time dependent horizontal force F kt acts on the block where k is a positive constant The acceleration time graph of the block is JEE Main ONLINE 2013 14 2 3 D 4

sphere of mass M is attached to a massless spring of spring contant K It can roll without slipping along a horizontal surface If the system is released after an initial stretch the time period is 1 2 3 2 2M K 7M SV O mooooooo 4 2 2 5M 3K 4 2 3M 2K

B Explain the following terms 1 Translatory motion 4 Displacement 2 Oscillatory motion 5 Average speed C Distinguish between the following 1 Translatory motion and rotatory motion 2 Distance and displacement 3 Uniform and non uniform motion 4 Mass and weight D Short answer questions 1 List any two types of motion 2 What is a scalar quantity Give an example 3 What is a vector quantity Give an example 4 Define weight What is its SI unit 3 Random motion 6 Weight

8 If percentage error in the measurement of radius of the sphere is 1 5 then the maximum percentage error in measurement of its volume is 1 3 3 4 5 2 1 5 4 6

The resultant of two vectors P and Q is R If Q is doubled then the new resultant vector is perpendicular to P Then R is equal to 2 Q 1 P Q 2PQ P 4 P Q P Q

4 1 What is the force between two small charged spheres having charges of 2 x 107C and 3 x 107C placed 30 cm apart in air

Two identical positive charges are placed on the y axis at y a and y a The variation of V electric potential along x axis is shown by graph V 1 3 V X 2 4 X

In the arrangement shown in Fig 1 24 the masses m of the bar and M of the wedge as well as the wedge angle a are known trolls The masses of the pulley and the thread are negligible The friction is absent Find the acceleration of the wedge M m Sa M Fig 1 24

a 5 If work W is done is blowing a bubble of radius R from soap solution then the work done in blowing a bubble of radius 2R from the same solution is a W 2 b 2W c 4W d 2 W

A conducting sphere of radius R carrying charge Q lies inside an uncharged conducting shell of radius 2R If they are joined by a metal wire A Q 3 amount of charge will flow from the sphere to the shell B 2Q 3 amount of charge will flow from the sphere to the shell C Q amount of charge will flow from the sphere to the shell kQ D amount of heat will be produced 4R

The moment of inertia of a semi circular area of radius r about the y axis is Ly c Tr 8 5 r4 b d RVW TI 4 64 r X

0 278 A truck is carry a box of mass m 50 kg on its flat horizontal rough surface with coefficient of friction 0 3 It is crossing a circular track of radius 27 m What is the maximum speed of the truck so that the box does not slide from the truck while moving on the circular path m 1 18 km hr 3 32 4 km hr R 2 36 km hr 4 None of these

11 Relative density of silver is 10 8 What is the density of silver in SI unit 5 izomm vlous 12 While floating in water part of volume of a wooden piece is immersed in water What is the 6 relative density of wooden piece 13 A piece of wood of uniform cross section and 15 cm height sinks 10 cm in water and 12 cm in

16 15 Two moles of a monatomic ideal gas undergo a cyclic process ABCDA as shown in figure BCD is a semicircle Find the efficiency of the cycle PA Id Povot Area 2po Po Po 2 I I 1 B A Vo C 2V V

The area bounded by the curves y loge x and y log x is a e 2 sq units e sq units c b 3 e sq units d e 1 sq units

22 A small plate of metal work function 1 17 eV is placed at a distance of 2 m from a monochromatic light source of wavelength 4 8 x 1077 m and power 1 0 W The light falls normally on the plate If a constant uniform magnetic field of strength 10 4T is applied parallel to the metal surface find the radius of the largest circular path followed by the emitted photoelectrons in m

Example 9 46 A horizontal force F acts on the hollow sphere at its centre as shown Coefficient of friction between ground and sphere is u What is maximum value of F for which there is no slipping O F f force of friction

15 assuming equal amplitudes gives mental s a cos at and s a cos w t 0 s are the one ency this ance ent ing nic ies 15 45 Here we have replaced the symbol y by s since we are referring to longitudinal not transverse displacement Let wo be the slightly greater of the two frequencies The resultant displacement is by the principle of superposition S S S a cosa t cos w t Using the familiar trignometric identity for cos A cosB we get ar ar t 2 which may be written as s 2 a cos w t cos w t 2 a cos COS and 2 az az t 2 If w w 1 w w w w th where 15 46 15 47 aj az 2 cca which means nation of the Shruti and Laya types Archaeologists date the Nelliappar temple to the 7th century and claim it was built by successive rulers of the Pandyan dynasty The musical pillars of Nelliappar and several other temples in southern India like those at Hampi picture Kanyakumari and Thiruvananthapuram are unique to the country and have no parallel in any other part of the world I asmen ut we can interpret Eq 15 47 as follows The resultant wave is oscillating with the average angular frequency however its amplitude is not constant in time unlike a pure harmonic wave The amplitude is the largest when the term cos at takes its limit 1 or 1 In other words the intensity of the resultant wave waxes and wanes with a frequency which is 20 0

Q9 Charges of 2 0 x 106 C and 1 0 x 106 C are placed at the corners A and B of a square of side 5 0 cm as shown in Fig How much work will be done in moving a charge of 1 0 x 10 C from C to D against the electric field D 91 5 cm C 5 cm 92

A simple camera with a converging lens of 60 mm focal length is focused on very far objects T focus the camera on a nearby object 1 5 m away the distance between the film and lens will have t be 2008 A decreased by 2 5 mm B increased by 2 5 mm C kept fixed as before but aperture increased by a factor of 2 5 D kept fixed as before hut aperture decreased by a factor of 2 5

15 Why is the emitter the base and the collector of a BJT doped differently 16 Which method of biasing is used for operating transistor as an amplifier

D In a common base connection the emitter current is 6 28mA and collector current is 6 20 mA Determine the common base DC current gain

3 Two bodies of masses 1 Kg and 2 Kg a connected by a metal wire shown in figur force of 10N is applied on the body of mas Kg The breaking stress of metal wini 2x10 Nm The minimum radius of the sin used if it is not to break IKg 1 0 23x10 m EKGF 10N 2 4x10m

A man generates a symmetrical pulse in a string by moving his hand up and down At t 0 the point in his hand moves downward The pulse travels with speed of 3 m s on the string his hands passes 6 times in each second from the mean position Then the point on the string at a distance 3m will reach its upper extreme first time at time t 1 1 25 sec Jution Frequency of wave Total time taken 2 3 3 3 3T 4 2 1 sec 3 T 1 s 3 VT 3 1 25 sec 3 13 12 sec 1m 4 none Ans 1

A point charge q is placed on the line AH and just outside the cube of side d at a distance of r r d Total flux of electric field through the surface ABCD ABCD is A q B q 168 C q 880 G H por B D 2010 D 9 q 168 goed

Two identical circular loops each of radius r carrying currents i and i are placed co axially at a small distance of separation d Find the force of interaction between them R PK