0
question_answer1) Is it possible that a body be in accelerated motion under a force acting on the body, yet no work is being done by the force. Give example.
question_answer2) Two protons are brought towards each other. Will the potential energy of the system decrease or increase ? If a proton and an electron be brought nearer, then?
question_answer3) Mountain roads rarely go straight up the slope, but wind up gradually. Why?
question_answer4) A light body and a heavy body have same linear momentum. Which one has greater K.E.?
question_answer5) A light body and a heavy body have same kinetic energy. Which one has greater linear momentum?
question_answer6) A truck and a car moving with the same K.E. are stopped by applying same retarding force by means of brakes. Which one will stop at a smaller distance?
question_answer7) A truck and a car are moving with the same K.E. on a straight road. Their engines are simultaneously switched off. Which one will stop at a lesser distance?
question_answer8) The velocity of an aeroplane is made twice (a) What will happen to the momentum? Will the momentum remain conserved ? (b) What will happen to the K.E ? Will the energy remain conserved?
question_answer9) In a thermal station, coal is used for the generation of electricity. Mention how energy changes from one form to the other before it is transformed into electrical energy?
question_answer10) Explain how fast moving neutrons can be quickly slowed down by passing them through water or heavy water. Or Hydrogenic materials are used as moderators in nuclear reactors to slow down the neutrons. Why?
question_answer11) What is the minimum energy released in the annhilation of an electron positron pair?
question_answer12) The heart rate (number of heart beats/minute) scales as 1/L, where L is the characteristic length of the mammal. (a) Can you explain this ? (b) The scale factor of a human relative to a monkey is about 2.5. What is the monkey's heart rate?
question_answer13) In a nerve impulse, about \[\text{1}{{0}^{\text{5}}}\] neutrons are fired. If energy associated with discharge of a single neutron is\[\text{1}{{0}^{-\text{1}0}}\text{J}\], estimate the energy used.
question_answer14) The absolute value of potential energy (and therefore total energy) has no physical significance. It is the difference of potential energies that matters. One can, therefore, add or subtract a constant to the potential energy (provided we do it to potential energy at every position for a given force) without any change in the physical situation. By convention, for forces which fall off to zero at large distances, the potential energy at infinity is taken to be zero. With this choice, is the potential energy positive or negative for (a) electron-positron bound state, (b) planet-satellite system, (c) electron-electron system?
question_answer15) A spring of force constant k is cut into two pieces of lengths \[{{l}_{1}}\] and \[{{l}_{2}}\]. Calculate force constant of each part.
question_answer16) If stretch in a spring of force constant k is doubled, calculate (a) ratio of final to initial force in the spring. (b) ratio of elastic energies stored in the two cases. (c) work done in changing to the state of double stretch.
question_answer17) The potential energy of two atoms separated by a distance x is given by \[U=-A/{{x}^{6}}\], where A is a positive constant. What is the force exerted by one atom on another atom?
question_answer18) Two coolies life some load from the road to the roof of a bus. One of them takes 1 min. and the other takes two min. to do the same job. Who has done more work and whose power is more?
question_answer19) A force is acting on a body moving along x-axis in the direction of motion of the body. If this force produces a potential energy \[U=A{{x}^{4}}\], where \[A=1.2J{{m}^{-4}}\], then what is the force acting on the body when the body is at x = -0.8 m.
question_answer20) Chemical, gravitational and nuclear energies are nothing but potential energies for different types of forces in nature. Explain this statement clearly with examples.
question_answer21) Two balls A and B of masses 0.3 kg and 0.2 kg respectively are moving along positive X-axis and negative X-axis with velocities 2.0 m/s. They collide and thereafter move in the directions opposite to their original directions. Find the velocities of A and B after collision. Also, calculate total K.E. of the balls before and after collision.
question_answer22) A bob of mass m attached to one end of a light rod hangs vertically. The rod is turned through \[\text{9}0{}^\circ \] so that it becomes horizontal and then released. Calculate the angle between the rod and vertical position at which the tension in the rod is equal to weight of the bob.
question_answer23) An object of mass 5kg is projected with a velocity of \[20\,m{{s}^{-1}}\]an angle \[{{60}^{o}}\]to the horizontal. At the highest point of its path, the projectile explodes and breaks up into two fragments of masses 1 kg and 4 kg. The fragments separate horizontally after the explosion, which releases internal energy such that K.E. of the system at the highest point is doubled. Calculate the separation between the two fragments when they reach the ground.
question_answer24) Fig. 4(HT).3 shows the transverse section of a hill. A ball of mass 0.5 kg is given a K.E. of 300J at A and rolls down to C. Assuming that there is no friction, calculate (i) K.E. of ball of B (ii) P.E. of ball of C, taking P.E. at A equal to zero (iii) speed of the ball at C; and (iv) change in P.E. in going from B to C. Take \[g=10\,m/{{s}^{2}}\]
question_answer25) A 100000 kg engine is moving up a slope of gradient 5° at a speed of 100 metre/hour. The coefficient of friction between the engine and the rails is 0.1. If engine has an efficiency of 4% for converting heat into work, find the amount of coal the engine has to burn in one hour. Burning of 1 kg coal yields 50000 J.
question_answer26) A block of mass 1.2 kg moving at a speed of 20 cm/s collides head-on with a similar block kept at rest. The coefficient of restitution is 3/5. Find the loss of Identic energy during the collision.
question_answer27) A 50g lead bullet, sp. Heat 0.02 is initially at \[{{30}^{o}}C\]. It is fired vertically upwards with a speed of 840 m/s and on returning to the starting level strikes a cake of ice at \[{{0}^{o}}C\]. How much ice is melted.
question_answer28) A person decides to use his bath tub water to generate electric power to run a 40 W bulb. The bath tub is located at a height of 10 m from the ground and it holds 200 litres of water. He installs a water driven wheel generator on the ground. At what rate shold the water drain from the bath tub to light the bulb? How long can he keep the bulb on, if bath tub was full initially? Efficiency of generator = 90%. Take \[g=9.8\,m/{{s}^{2}}\].
question_answer29) A massless platform is kept on a light elastic springy as shown in Fig. 4(HT).5. When a stone of 0.1 kg mass is dropped on the pan from a height of 0.24 m, the spring compresses by 0.01 m. From what height should the stone be dropped to cause a compression of 0.04 m?
question_answer30) In the \[\beta \] decay of\[N{{a}^{24}}\], the combined electron neutrino momentum has a magnitude equal to 4 MeV/c. What is the recoil energy of the daughter nucleus, given that its mass is 23.99 u? Take.
question_answer31) Two cylindrical vessels of equal cross-sectional area A contain water upto heights \[{{h}_{1}}\]and \[{{h}_{2}}\].The vessels are interconnected so that the levels in them become equal. Calculate the work done by the force of gravity during the process. The density of water is \[\rho \].
question_answer32) a block of mass m is pushed against a spring of spring constant k fixed at one end to a watt. The block can slide on a frictionless table as shown in Eig.4(HT).8. The natural length of the spring is lq and it is compressed to half its natural length when the block is released. Find the velocity of the block as a function of its distance x from the wall.
question_answer33) Fig. 4(HT).9 shows a loop-the-loop track of radius r. A car (without engine) starts from a platform at a distance h above the top of the loop and goes around the loop without falling off the track. Find the minimum value of h for a successful looping. Neglect friction.
question_answer34) A particle of mass m moving eastward with a velocity V collides with another particle of same mass moving northwards with the same speed V. The two particles coalesce and the new particle moves in NE direction. Calculate magnitude and direction of velocity of new particle.
question_answer35) A solid ball of density half that of water falls freely under the gravity from a height of 19.6 m and then enters water. Upto what depth will the ball go? How much time will it take to come again to the water surface? Neglect air resistance and Viscosity of water, \[\left( \text{g }=\text{ 9}\text{.8 m}/{{\text{s}}^{\text{2}}} \right)\].
question_answer36) A shot fired from a cannon explodes in air. What will be the changes in the momentum and the kinetic energy?
question_answer37) Explain with reason whether the potential energy in the following cases increases or decreases: (a) a spring is compressed, (b) a spring is stretched, (c) two dis-similar charges are brought near each other, (d) a body is taken away against the gravitational force, (e) air bubble rises up in water.
question_answer38) The protons are brought towards each other. Will the potential energy of the system decrease or increase? If a proton and an electron be brought nearer, then?
question_answer39) Two springs A and B are identical but A is harder than \[\text{B}\left( {{\text{K}}_{\text{A}}}>{{\text{K}}_{\text{B}}} \right)\]. On which spring more work will be done if : (a) they are stretched through the same distance, (b) they are stretched by same force?
question_answer40) A man rowing a boat upstream is at rest with respect to shore, (a) Is he doing any work? (b) If he stops rowing and moves down with the stream, is any work being done on him?
question_answer41) A pump motor is used to deliver water at a certain rate from a given pipe. To obtain 'n' times water from the same pipe in the same time by what amount (a) the force and (b) power of the motor should be increased.
question_answer42) A spring is compressed by tieing its ends together tightly. It is then placed in acid and dissolves. What happens to its stored potential energy.
question_answer43) (a) Two masses one n times heavier than the other are dropped from same height. How do their momentum compare just before they hit the ground? (b) Two masses one n times heavy as the other have equal kinetic energy. How do their momentum compare?
question_answer44) (a) Can kinetic energy of a system be changed without changing its momentum? (b) Can momentum of a system be changed without changing its kinetic energy?
question_answer45) A meteorite burns in the atmosphere before it reaches earth's surface. What happens to its momentum?
question_answer46) Can a body have momentum without energy?
question_answer47) Can a body have energy without momentum?
question_answer48) The momentum of a body is increased by 50%. What is the percentage change in its K.E.?
question_answer49) Can a body have momentum when its energy is negative?
question_answer50) The potential energy function for a particle executing simple harmonic motion is given by\[V(x)=\frac{1}{2}k{{x}^{2}}\], , where k is the force constant of the oscillator. For\[k=\frac{1}{2}N{{m}^{-1}}\] , show that a particle of total energy 1 joule moving under this potential must turn back when it reaches \[x=\pm 2m\].
question_answer51) A stone is dropped from the top of a high tower. Will the mechanical energy of the stone be conserved or not if the force of friction due to air is not neglected?
question_answer52) Fig. 4.46 shows two smooth inclined planes with different inclinations. Two blocks of same mass are allowed to slide down the two planes from the top A. Which block will arrive on the ground with greater velocity?
question_answer53) A man can jump higher on moon than on earth. With same effort, can a runner improve his timing for 100 m race on moon as compared to that on earth?
question_answer54) A force F is related to the position of a particle by the relation . Find the work done by the force when the particle moves from \[x=2m\] to \[x=4m\].
question_answer55) The nucleus\[F{{e}^{57}}\]emits a ray of energy 14.4 keV. If the mass of the nucleus is 56.935 u, calculate the recoil energy of nucleus.
question_answer56) Two identical 5kg blocks are moving with same speed of 2m/s towards each other along a frictionless horizontal suface. The two blocks collide, stick together and come to rest. Consider the two blocks as a system. Calculate work done by (i), external forces and (ii), internal forces.
question_answer57) A bullet of mass 0.01kg and travelling at a speed of 500 m/s strikes a block of mass 2kg which is suspended by a string of length 5 m. The centre of gravity of the block is found to rise a vertical distance of 0.1 m, Fig. 4.47. What is the speed of the bullet after it emerges from the block? \[\left( g=9.8\,m/{{s}^{2}} \right)\].
question_answer58) Two springs have force constants \[{{\text{K}}_{\text{1}}}\]and \[{{\text{K}}_{\text{2}}}\left( {{\text{K}}_{\text{1}}}>\text{ }{{\text{K}}_{\text{2}}} \right)\]. On which spring is more work done when they are stretched by the same force?
question_answer59) Show that (\[\text{A }={{(\vec{A}.\vec{A})}^{1/2}}\]
question_answer60) If\[\vec{A}\,.\,\vec{B}=\vec{B}\,.\,\vec{C}\], is it correct to conclude that \[\vec{A}=\vec{C}\]?
question_answer61) The dot product of two vectors vanishes when vectors are orthogonal and has maximum value when vectors are parallel to each other. Explain.
question_answer62) What is work done in holding a 15 kg suitace while waiting for a bus for 15 minutes?
question_answer63) Is it practically possible to have situations where \[(E-V)<0\]?
question_answer64) Can K.E. of a system be increased or decreased without applying any external force on the system?
question_answer65) Give some example where a force does work on a body but fails to change its K.E.
question_answer66) Does the sun do any work on earth, when earth revolves around the sun in a perfectly circular orbit?
question_answer67) Does K.E. depend upon the direction of motion involved? Can it be negative? Does its value depend on frame of refrence?
question_answer68) Name the largest and smallest practical unit of energy.
question_answer69) Is work done by a non conservative force always negative? Comment.
question_answer70) Is linear momentum of a system always conserved?
question_answer71) 'The collision between two hydrogen atoms is perfectly elastic, so the momentum is conserved'. Do you agree with this statement?
question_answer72) A ball of mass m moving with vel. v strikes head on elastically with a number of balls of same mass at rest in a line. Only one ball from other side moves with same velocity. Explain why not two balls move simultaneously, each with vel. v/2?
question_answer73) Is it possible to have a collision in which the whole of KE is lost?
question_answer74) If two objects collide and one is initially at rest (a) is it possible for both to be at rest after collision ? (b) is it possible for any one to be at rest after collision?
question_answer75) What should be the angle between the force and the displacement for maximum and minimum work?
question_answer76) Does potential energy of a spring decrease/increase when it is compressed or stretched?
question_answer77) When an air bubble rises in water, what happens to its potential energy?
question_answer78) In which, elastic or inelastic collision, the momentum is conserved? What about K.E.?
question_answer79) In which motion, momentum changes but K.E. does not?
question_answer80) A shot fired from a cannon explodes in the air. What will be the changes in momentum and K.E.?
question_answer81) Out of joule, calorie, kilowatt and electron volt, which one is not the unit of energy?
question_answer82) The momentum of an object is doubled. How does its K.E. change?
question_answer83) Can RE. of an object be negative?
question_answer84) Does the work done in moving a body depend on how fast or how slow the body is moved?
question_answer85) What type of energy is stored in the spring of a watch?
question_answer86) A spring is cut into two equal halves. How is the spring constant of each half affected?
question_answer87) Does kinetic energy depend on the direction of motion involved ? Can it be negative ? Does it depend on frame of reference?
question_answer88) Can kinetic energy of a system be increased or decreased without applying any external force on the system?
question_answer89) Is it possible to exert a force which does work on a body without changing its kinetic energy ? If so, give example.
question_answer90) In case of a moving body, as force of friction is m mg, can we regard m mg x as potential energy similar to mgh?
question_answer91) A ball of mass m moving with vel. \[\upsilon \]strikwa head on elastically with a number of balls of same mass at rest in a line. Only one ball from other side moves with same velocity. Explain why not two balls move simultaneously, each with vel. \[\upsilon /2\]?
question_answer92) Is it possible to have a collision in which the whole of K.E. is lost?
question_answer93) If two objects collide and one is initially at rest (a) is it possible for both to be at rest after collision? (b) Is it possible for any one to be at rest after collision?
question_answer94) In which, elastic or inelastic collision, the momentum is conserved? What about K.E.?
question_answer95) If \[\vec{A},\,\,\vec{B}\]and\[\vec{C}\] are non-zero vectors and \[\vec{A}.\,\,\vec{B}\,\,=0\] and\[\vec{B}\,.\,\vec{C}=0\], then find out the value of \[\vec{A}\].\[\vec{C}\]
question_answer96) The sum and difference of two vectors are perpendicular to each other. Prove that the vectors are equal in magnitude.
question_answer97) Can the scalar product of two vectors be negative?
question_answer98) If \[\vec{A}\], \[\vec{B}\] and \[\vec{C}\] are mutually perpendicular vectors, then find the value of \[\vec{A}\].(\[\vec{B}\]+\[\vec{C}\]).
Please Wait you are being redirected....
You need to login to perform this action.You will be redirected in 3 sec
OTP has been sent to your mobile number and is valid for one hour
Your mobile number is verified.