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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1301. |
When a ball is thrown up , the magnitude of its momentum decreases end then increase . Does this violate the conervation of momenturn priaciple ? |
| Answer» No , An extenal force , the gravitational pull of earth , is acting on the bell which is repcesible for the change in moment | |
| 1302. |
A force shown in the `F-x` graph is applied to a `2kg` block horizontal as shown in figure. The change in kinetic energy is A. `15 J`B. `20 J`C. `25 J`D. `30 J` |
| Answer» Change in kinetic energy `Deltak=(1)/(2)xx(10-2)xx5=20J` | |
| 1303. |
Kinetic energy of a particle is increased by `1%`. By how much percentage momentum of the particle will increase ? |
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Answer» `p=sqrt(2Km)` or `Pprop K^(1/2)` For small `%` changes, `%` change in `p=1/2`(`%`change in `K`) `=1/2(1%) =0.5%`. |
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| 1304. |
A bob of mass m is suspended by a light string of length L. It is imparted a horizontal velocity `v_(0)` at the lowest point A such that it completes a semi-circular trajectory in the vertical plane with the string becoming slack on reaching the topmost point C, figure, Obtain an expression for (i) `v_(0)` (ii) the speeds at points B and C, (ii) the ration of kinetic energies `(K_(B)//K_(C))` at B and C. Comment on the nature of the trajectory of the bob after it reahes the poing C. |
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Answer» There are two external forces on the bob `:` gravity (mg) and tension (T) in the string. The tension does no work as displacement is always perpendicular to the string. Total mechanical energy (E) of the system is conserved. If we take P.E. of the system to be zero at the lowest point A, then At A, `E=(1)/(2)mv_(0)^(2)` ...(i) The necessary centripetal force `mv_(0)^(2)//L` is provided by `(T_(A)-mg)`. `T_(A)-mg=(mv_(0)^(2))/(L)` ...(ii) At the highest point C, the string slackens as the tension in the string `(T_(c))` becomes zero. `:.` At C, `mg=(mv_(C)^(2))/(L)` ...(iii) and total energy, `E=(1)/(2)mv_(C)^(2)+mg(2L)` ...(iv) From (iii), `v_(C)=sqrt(gL)` ...(v) From (iv), `E=(1)/(2)m(gL)+2mgL=(5)/(2)mgL` Using (i), `(1)/(2)mv_(0)^(2)=(5)/(2)mgL, v_(0)=sqrt(5gL)` ...(vi) At B, the energy is `E=(1)/(2)mv_(B)^(2)+mg(L)` or `(1)/(2)mv_(B)^(2)=E-mg(L)=(5)/(2)mgL-mgL` `=(3)/(2)mgL` `v_(B)=sqrt(3gL)` `(K_(B))/(K_(C))=((1)/(2)mv_(B)^(2))/((1)/(2)mv_(C)^(2))=(3gL)/(gL)=(3)/(1)` At C, the string becomes slack and the velocity of the bob is horizontal and to the left. Therefore, the bob will continue on its circular path and complete the revolution. |
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| 1305. |
Four smooth steel balls of equal mass at rest are free to move along a straight line without friction. The first ball is given a velocity of 0.4 m/s . It collides head on with the second elastically, the second one similarly with the third and so on. The velocity of the last ball isA. 0.4m/sB. 0.2m/sC. 0.1m/sD. 0.05m/s |
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Answer» Correct Answer - A |
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| 1306. |
A set of n identical cubical blocks lies at rest parallel to each other along a line on a smooth horizontal surface. The separation between the near surfaces of any two adjacent blocks is L . The block at one end is given a speed v towards the next one at time 0 t . All collisions are completely inelastic, thenA. The last block starts moving at `t=((n-1)L)/(v)`B. The last block starts moving at `t=(n(n-1)L)/(2v)`C. the centre of mass of the system will have a final speed vD. The centre of mass of the system will have a final speed `(v)/(n)`. |
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Answer» Correct Answer - B::D |
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| 1307. |
A mass of `0.5 kg` moving with a speed of `1.5 m//s` on a horizontal smooth surface, collides with a nearly weightless spring of force constant `k =50 N//m` The maximum compression of the spring would be.A. 0.15 mB. 0.12 mC. 1.5 mD. 0.5 m |
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Answer» Correct Answer - A |
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| 1308. |
Two identical blocks `A` and `B` , each of mass `m` resting on smooth floor are connected by a light spring of natural length `L` and spring constant `k`, with the spring at its natural length. A third identical block `C` (mass `m`) moving with a speed `v` along the line joining `A` and `B` collides with `A`. The maximum compression in the spring isA. `vsqrt((m)/(2k))`B. `msqrt((v)/(2k))`C. `sqrt((mv)/(k))`D. `(mv)/(2k)` |
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Answer» Correct Answer - A |
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| 1309. |
If the K.E. of a particle is doubled, then its momentum willA. Remain unchangedB. Be doubledC. Be quadrupledD. Increase `sqrt(2)` times |
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Answer» Correct Answer - D |
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| 1310. |
If force and displacement of particle in direction of force doubled. Work would beA. DoubleB. 4 timesC. halfD. `(1)/(4)` times |
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Answer» Correct Answer - B |
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| 1311. |
The KE acquired by a mass m in travelling a certain distance s, starting from rest, under the action of a constant force is directly proportional to :A. `sqrt(m)`B. independent of mC. `1//sqrt(m)`D. m |
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Answer» Correct Answer - B |
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| 1312. |
If a man increase his speed by 2m/s, his K.E. is doubled, the original speed of the man isA. `(1+2sqrt(2))m//s`B. `4m//s`C. `(2+2sqrt(2))m//s`D. `(2+sqrt(2))m//s` |
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Answer» Correct Answer - C |
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| 1313. |
Assertion : A kinetic energy of a body is quadrupled, when its velocity is doubled. Reason : Kinetic energy is proportional to square of velocityA. If both assertion and reason are true and the reason is the correct explanation of the assertionB. If both assertion and reason are true but reason is not the correct explanation of the assertionC. If asserti on is true but reason is falseD. If the assertion and reason both are false |
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Answer» Correct Answer - A |
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| 1314. |
Assertion : A body cannot have energy without possessing momentum but it can have momentum without having energy. Reason : Momentum and energy have same dimensions.A. If both assertion and reason are true and the reason is the correct explanation of the assertionB. If both assertion and reason are true but reason is not the correct explanation of the assertionC. If asserti on is true but reason is falseD. If the assertion and reason both are false |
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Answer» Correct Answer - D |
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| 1315. |
Define the conservative and non-conservative forces. Give examples of each. |
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Answer» Conservative force : e.g., Gravitational force, electrostatic force. Non-Conservative force : e.g., forces of friction, viscosity. |
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| 1316. |
What is Energy ? |
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Answer» The energy of a body is defined as its capacity for doing work. (1) It is a scalar quantity. (2) Dimension : [ML2T2] it is same as that of work or torque. (3) Units : Joule [S.I.], erg [C.G.S.] Practical units : electron volt (eV), Kilowatt hour (KWh), Calories (Cal) Relation between different units : 1 Joule = 107 erg 1 eV = 1.6 × 10–19 Joule 1 KWh = 3.6 × 106 Joule 1 Calorie = 4.18 Joule |
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| 1317. |
Differentiate between conservative and non-conservative forces. |
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Answer» Conservative force: A force is conservative (i) if the work done by the force in displacing a particle from one point to another is independent of the path followed by the particle and (ii) if the work done by the force in moving a particle around any closed path is zero. Examples : Gravitational force, electrostatic force and elastic force of a spring are all conservative forces. Non-conservative force: If the amount of work done in moving an object against a force from one point to another depends on the path along which the body moves, then such a force is called a non-conservative force. Examples : Forces of friction and viscosity are non-conservative forces. |
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| 1318. |
A foce acts on a 30.g particle in such a way that the position of the particle as a function of time is given by `x=3t-4t^(2)+t^(3)`, where x is in metre and t in second. The work done during the first 4s isA. 5.28 JB. 450 mJC. 490 mJD. 530 mJ |
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Answer» Correct Answer - A |
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| 1319. |
Differentiate between Stable, Unstable and Neutral equilibrium. |
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| 1320. |
Define Collision. Give its types. |
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Answer» Collision is an isolated event in which a strong force acts between two or more bodies for a short time as a result of which the energy and momentum of the interacting particle change. Types of collision : (i) Perfectly Elastic collision (ii) Inelastic collision (iii) Perfectly inelastic collision |
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| 1321. |
What are the types of Potential Energy equilibrium ? |
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Answer» If net force acting on a particle is zero, it is said to be in equilibrium. For equilibrium, dU/dx = 0, but the equilibrium of particle can be of three types : (i) Stable equilibrium (ii) Unstable equilibrium (iii) Neutral equilibrium |
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| 1322. |
Define Mass energy equivalence. |
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Answer» The relation between the mass of a particle m and its equivalent energy is given as E = mc2 where c = velocity of light in vacuum. |
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| 1323. |
Define Kinetic Energy. |
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Answer» The energy possessed by a body by virtue of its motion is called kinetic energy. Let m = mass of the body, v = velocity of the body then K.E. = 1/2 mv2 |
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| 1324. |
What is Potential Energy? Give its types. |
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Answer» Potential energy is defined only for conservative forces. In the space occupied by conservative forces every point is associated with certain energy which is called the energy of position or potential energy. Potential energy generally are of three types : (i) Elastic potential energy (ii) Gravitational potential energy (iii) Chemical potential energy |
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| 1325. |
Does Kinetic energy depends on frame of reference ? |
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Answer» The kinetic energy of a person of mass m, sitting in a train moving with speed v, is zero in the frame of train but 1/2 mv2 in the frame of the earth. |
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| 1326. |
Why is electrical power required at all when the elevatore is descending ? Why should there be a limit on the number of passengers in this case ? |
| Answer» Electric power is required to prevent the elevator from falling freely under gravity. Limit on the number of passengers in this case is needed again to prevent the elevator from descending with large velocity. | |
| 1327. |
A ball is released from certain height. It loses 50% of its kinetic energy on striking the ground. It will attain a height again equal toA. One fourth the initial heightB. Half the initial heightC. Three fourth initial heightD. None of these |
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Answer» Correct Answer - B |
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| 1328. |
It takes a block twice as long to slide down a plane incline at `45^(@)` to the horizontal as it would take for it to slide down the same plane had the plane been frictionless. Colculate the coefficient of friction between block and inclined plane. |
| Answer» Correct Answer - `0.75.` | |
| 1329. |
A body just droppeed from a tower explodes into two placed of equal mass in mid -air which of the following is not posible?A. Each part will follow parabolic pathB. Only one part will follow parabolic pathC. Both part move along a verticle lineD. One part reaches the ground earlier than the other |
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Answer» Correct Answer - B If the velocities acquired due to explosions are in vertical direction, then option `C and D` are possible . If one of them possible. If one of them follows parabolic path (or acquires velocity in horizontal direction), them other also has to follow parabolic path (or acquires velocity in horizontal direction to keep the momentum zero in horizontal direction ). Hence, option `B` can never be possible. |
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| 1330. |
A system comprises of two small spheres with the same masses `m`. initially, the spring is non deformed. the spheres set in motion in a gravity space at the velocities as shown in the diagram. The maximum elastic potential energy stored in the system isA. `(mv_(0)^(2))/(2sqrt(2))`B. `mv_(0)^(2)`C. `(1)/(2)mv_(0)^(2)`D. `2mv_(0)^(2)` |
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Answer» Correct Answer - B Both sphers will come at rest simuiltaneously because net momentum of system is zero And when they comes to rest their `KE` convets into clastic potential energy of spring `U = 2 [(1)/(2) mv_(0)^(2)] = mv_(0)^(2)` |
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| 1331. |
Assertion : In case of bullet fired from gun, the ratio of kinetic energy of gun and bullet is equal to ratio of mass of bullet and gun. Reason : In firing, momentum is conservedA. If both assertion and reason are true and the reason is the correct explanation of the assertionB. If both assertion and reason are true but reason is not the correct explanation of the assertionC. If asserti on is true but reason is falseD. If the assertion and reason both are false |
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Answer» Correct Answer - A |
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| 1332. |
Assertion: Power of machine gun is determined by body both the number of bullet fired per secondand kinetic energy of bullets. Reason: Power of any machine is defined as work done(by it) per unit time.A. If both assertion and reason are true and the reason is the correct explanation of the assertionB. If both assertion and reason are true but reason is not the correct explanation of the assertionC. If asserti on is true but reason is falseD. If the assertion and reason both are false |
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Answer» Correct Answer - A |
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| 1333. |
If a body of mass 10 kg is raised to a height of 6 m above the earth, calculate its potential energy. |
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Answer» Potential energy of the body = mgh Mass of body = 10 kg Height above the earth = 6 m Acceleration due to gravity = 10 m/s2 So, EP = 10 × 10 × 6 = 600 J Thus, potential energy of the body is 600 Joules. |
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| 1334. |
The system shown in the figure consider of a light , inextenslible cord, light, frictionless pulley, and blocks of equal mass. Notice that block `B` is attached to one of the pulleys. The system is initial held at rest so that the ground . The blocks are then released. Find the speed of block `A` at the moment the vertical separation of the blocks is `h`. A. `sqrt((6 gh)/(15))`B. `sqrt((8 gh)/(13))`C. `sqrt((8 gh)/(15))`D. `sqrt((6 gh)/(13))` |
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Answer» Correct Answer - B When block `B` moves up by `1 cm` block `A` moves down by the `2 cm` and the sepration becomes `3 cm` . We then choose the final point to be when `B` has moved by `(h)/(3)` and has speed `(v_(A))/(2)`. Then `A` has moved down `(2h)/(3)` and has speed `v_(A)` : `Delta K + Delta U = 0` `(K_(A) + K_(B) +(U_(g))_(f) - (K_(A) +(K_(B) +U_(g))_(i) = 0` `(K_(A) +K_(B) + U_(g))_(i) +(K_(A) +(K_(B) + U_(g))_(f)` `0 + 0 + 0 = (1)/(2) mv_(A)^(2) + (1)/(2)m ((v_(A))/(2))^(2) + (mgh)/(3) - (mg 2h)/(3)` `(mgh)/(3) = (5)/(8) mv_(A)^(2) implies v_(A) = sqrt((8gh)/(15))` |
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| 1335. |
An object of mass 15 kg is moving with uniform velocity of 4 m/sec. What is the kinetic energy possessed by it ? |
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Answer» Mass of the object, m = 15 kg Velocity of the object, v = 4 m/s Ek = 1/2mv2 = 1/2 × 15 kg × 4 ms-1 × 4 ms-1 = 120 J The kinetic energy of the object is 120 J. |
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| 1336. |
A spring is held correspessed so that its stored energy is `2.4 J`. Its ends are in constant with masses `1 g and 48 g` placed on a frictionless table. When the spring in released, the heaveier mass will acquire a speed of:A. `(2.4)/(49)` ms^(-1)`B. `(2.4 xx 48)/(49) ms^(-1)`C. `mu mgh//sin theta`D. `(10^(6))/(7)`c ms^(-1)` |
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Answer» Correct Answer - C `(1)/(2)m_(1)v_(1)^(2) + (1)/(2) m_(2) v_(2)^(2) = 2.4` or `m_(1)v_(1)^(2) + m_(2) v_(2)^(2) = 4.8`…(i) Now `m_(1)v_(1)= m_(2)v_(2)` or `v_(1) = 48v_(2)` Using (i) `(1)/(1000) (48v_(2))^(2) + (48)/(1000) v_(2)^(2) = 4.8` or `v_(2) = (10)/(7) m//s = (10^(2))/(7) cm//sec`. |
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| 1337. |
While running a person transforms about `0.60 J` chemical energy to mechanical energy per stop per kilogram of body mass. If a `60 kg` runner transform energy at a rate of `72 W` during a race, how fast is the person running? Assume that a running step is `1.5m` longA. `2.0 m//s`B. `3.0 m//s`C. `2.5 m//s`D. `sqrt((6 gh)/(13))` |
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Answer» Correct Answer - D We first determine the energy output of the runner: `= (0.60 J//kg - step) (60 kg) ((1 step)/(1.50 m)) = 24.0 J//m` From this we calculate the force exerted by the runner per step: `F = (24 J//m) (1 N.m//J) = 24 N` |
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| 1338. |
Write the main properties of potential energy. |
Answer»
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| 1339. |
Alex and john are loding adentical cabinates onto a truck .Alex lifts his cabinet strainght up from the ground to the bed of the truck , whereas john slides his cabinet up a rough ramp to the truck .which statement correct about the work on the cabinet- Earth system ?A. Alex and john do the same amount of workB. Alex does more work then johnC. john does more work then alexD. None of those statement is necessarily true because the force the friction is unknown |
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Answer» Correct Answer - C Assuming that the cabinate has negligible speed during the operition , all of the work Alex does is used in inc reasing the gravitational potential energy of the cabitane - earth system .However in addition to increasing the gravitational potential energy of the cabitane - earth system by the same amount as Alex did . John must do work overcoming the friction between the cabinet and ramt . This means the total work done by john is greater than that done by Alax . |
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| 1340. |
A 12 HP motor has to be operated 8 hours / day . How much will it cost at the rate of 50 paisa / kWh in 10 daysA. Rs 350/-B. Rs.358/-C. Rs.375/-D. Rs.397/- |
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Answer» Correct Answer - B |
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| 1341. |
A prismatic block of mass m is lifted through a distanced along the slant. If the coefficient of friction between the block and slant surface is 1`mu.` find the (A) Work done by force F, friction and gravity. (B) Speed of the block after moving through a distance d. Assuming,` mu=1//6,theta=45%^(@)and F=2mg` |
| Answer» `(A) sqrt2mgd,-(mgd)/(2sqrt2),(-mgd)/(sqrt2),(B)sqrt((gd)/(sqrt2))` | |
| 1342. |
A spring-mass system ( `m_1` + massless spring + `m_2`) fall freely from a height `h` before `m_2` colliding inelastically with the ground. Find the minimum value of `h` so that block `m_2` will break off the surface. Assume k=stiffness of the spring. |
| Answer» `(m_(2)(2m_(1)+m_(2)))/(2m_(1)k)` | |
| 1343. |
A car starts from rest and moves on a surface in which the coefficient of friction between the road and the tyres increases linearly with distance (x). The car moves with the maximum possible acceleration. The kinetic energy (E) of the car will depend on x asA. `Eprop(1)/(x^(2))`B. `Rprop""(1)/(x)`C. `E prop x`D. `E prop x^(2)` |
| Answer» Correct Answer - D | |
| 1344. |
What is the potential energy when it is at a height of 2m from the ground? What is the total energy now? |
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Answer» Potential energy at 2m height U = mgh = 15 × 10 × 2 = 300J ∴ Total energy = 300 + 300 = 600J |
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| 1345. |
Calculate the potential energy of a body of mass 1 kg at a height of 6m from the ground? |
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Answer» Mass m = 1 kg, Acceleration due to gravity g = 10m/s2 h = 6 m, U = mgh = 1 × 10 × 6 = 60J |
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| 1346. |
While the flower pot is falling down, what forms of energy does it possess? |
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Answer» potential energy and kinetic energy |
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| 1347. |
What is the kinetic energy of the flower pot just before it touches the ground? |
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Answer» K = \(\frac{1}{2}\) mv2 v2 = u2 + 2as = 0 + 2 x 10 x 4 = 80 Kinetic energy K = \(\frac{1}{2}\) mv2 = 1/2 × 15 × 80 = 600J In ethene, There is carbon – carbon double bond |
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| 1348. |
While falling, when the flower pot is at a height of 2m from the ground, what will be its kinetic energy? |
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Answer» K = \(\frac{1}{2}\) mv2 u = 0, g = 10m/s2, s = 4 – 2 = 2m v2 = u2 + 2as = 0 + 2 × 10 × 2 = 40 K = 1/2 × 15 × 40 = 300J |
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| 1349. |
Write down situations in which potential energy varies. |
Answer»
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| 1350. |
What form of energy does the flower pot have when it is on the sunshade of a building? |
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Answer» Potential energy |
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