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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.
| 13151. |
A metre stick is balanced on a knife edge at its centre when two coins, each of mass 5g are put one on top of the other at the 12 cm mark. The stick is found to be balaced at 45 cm. What is the mass of the metre stick ? |
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Answer» Solution :SINCE stick is in rotational EQUILIBRIUM, the total torque of all the forces about the resultant .R. is zero. TAKING the turning effects about the point of ACTION of the resultant .R. we have `10gxx33=mgxx5` on solving m=66 G 
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| 13152. |
In the above case, if P_(1), P_(2) and P_(3) are their final pressure's. Then |
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Answer» <P>`P_(2)GT P_(1)gt P_(3)` |
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| 13153. |
A block of weight 100N is pushed by a force F on a horizontal rough plane moves with an acceleration 1 m//s^(2), when force is doubled its acceleration becomes 10m//s^(2). The coefficient of friction is _______ (g=10 ms^(-2)) |
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Answer» `0.2` |
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| 13154. |
A string of mass per unit length muis clamped at both ends such that one end of the string is atx = 0and the other end is at x = l . When string vibrates in fundamental mode amplitude of the mid point O of the string is a and tension in thestring is T .Find the total oscillation energy stored in the string. |
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| 13155. |
Which physical quantities are expressed by the following ? (a) rate of change of angular momentum(b) moment of momentum |
| Answer» SOLUTION :(a) TORQUE, (B) ANGULAR MOMENTUM | |
| 13156. |
Two satellites are revolving round the earth at different heights. The ratio of their orbital speeds is 2 : 1. If one of them is at a height of 100 km, what is the height of the other satellite ? |
| Answer» SOLUTION :19,300 KM | |
| 13157. |
State and explain the principle of moments. |
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Answer» Solution :(i) Sum of the clockwise moments is EQUAL to sum of the anticlockwise moments when a BODY is in ROTATIONAL equilibrium or algebraic sum of moments at any point is zero. (ii) Consider a LIGTH rod of negligible mass which is pivoted at a point along its length. Let two parallel forces `F_(1) and F_(2)` act at the two ends at distances `d_(1) and d_(2)` from the point of pivot and the normal reaction force N at the point of pivot as shown in Figure. (iii) If the rod has to remain stationary in horizontal position, it should be in translational and rotational equilibrium. Then, both the net force and net torque must be zero.  For net force to be zero, `- F_(1) + N - F_(2) = 0` `N = F_(1) + F_(2)` For net torque to be zero, `d_(1) F_(1) - d_(2) F_(2) = 0` `d_(1)F_(1) = d_(2)F_(2)` The above equation represents the PRINCIPLE of moments. |
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| 13158. |
A metal plate of mass 200g is balanced in mid air by throwing 40 balls per second , each of mass 2g vertically upward from below . The balls get rebounded with the same speed with which they strike the plate . Find the speed with which the balls strike the plate. |
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| 13159. |
The time period of simple pendulum of length L as measured in a lift descending with acceleration g/3ms^-2 is....... |
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Answer» `2pisqrt((3l)/(2g))` |
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| 13160. |
Choose the correct statement a. Any motion that reqeats itself in equal intervals of time along the same path is called periodic motion. b. The displacement of a particle in periodic motion can always ve expressed in terms of sine and cosine functions of time. c. A body in periodic motion moves back and forth over the same path is called oscillatory or vibrating motion. d. Simple harmonic motion is a particular case of periodic motion. |
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Answer» Only a, B, d are TRUE |
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| 13161. |
Mention the SI unit of mass and weight. |
| Answer» Solution :SI unit of MASS (m) is kg. SI unit of weight (W) is Newton (N). | |
| 13162. |
An unhappy mouse of mass m_(0) moving on the end of a spring of spring constant p is acted upon by a damping force F_(x) = -b vartheta_(x) For what value of b the motion is critically damped ? |
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Answer» `B = SQRT((p)/(m_(0)))` |
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| 13163. |
If the ratio of principal specific heat capacities of a certain gas is 1:4 and its density at STP is 0.09 kgm^(-3)calculate the values of specific heat capacity at constant pressure and constant volume. [Standard atmospheric pressure =1.01 xx 10 ^(5) Nm ^(-2) |
| Answer» Solution :`R = P // RHO T = 1.01 XX 10 ^(5) //0.09 xx 273 = 411.7 J KG ^(-1) K ^(-1) C _(v) = r//gamma -1 = 10276.76 J kg ^(-1) K ^(-1).` | |
| 13164. |
The particle of mass 1 kg is projected with velocity 20sqrt(2)m/s at 45^(@) with ground . When , the particle is at highest point (g=10 m//s^(2)), |
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| 13165. |
Power applied to a particle varies with time as P(3t^(2)-2t+1)watt, where t is in second. The change in its kinetic energy between time t=2 sec. and t=4 sec. is |
| Answer» ANSWER :B | |
| 13166. |
What is an angle between two equal bodies of same mass one of them is rest and experiences oblique collision to each other ? |
| Answer» SOLUTION :`90^(@)` | |
| 13167. |
If P, v and E denotes the momentum, velocity and K.E. of a particle then ...... |
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Answer» `p=(d^(2)E)/(dt^(2))` |
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| 13168. |
The below P-V diagram represents the thermodynamic cyclic of an engine, operating with and ideal monoatomic gas. The amount of heat extracted from the source in a single cycle is |
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Answer» <P>`[13/2]P_(0)V_(0)` |
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| 13169. |
A cricket player throws the ball to have maximum horizontal range of 120 m. If the throws the ball vertically with same velocity what is the maximum height it can reach? |
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| 13170. |
Is the mechanical energyalways conserved ? |
| Answer» SOLUTION :No , it is conservedwhen the FORCES INVOLVED are CONSERVATIVE in NATURE . | |
| 13171. |
A satellite moves round the earth in a circular orbit of radius R making one revolution per day. A second satellite moving in a circular orbit, moves round the earth one in 8 days. The radius of the orbit of the second satellite is |
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Answer» Solution :Given that, `T_(1) =1` DAY and `T_(2) =8` days `:. (T_(2))/(T_(1))=((r_(2))/(r_(1)))^(3//2)` `rArr (r_(2))/(r_(1))=((T_(2))/(T_(1)))^(2//3)=((8)/(1))^(2//3)=4 rArr r_(2)=4r_(1)=4R`. |
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| 13172. |
Handle of the door is always kept on other side (far side) of the hinge. Why? |
| Answer» Solution :Because as `vecr` increase `vectau` also increase and rotational motion also increase and for MINIMUM (LEAST) force is needed to open or close the DOOR. | |
| 13173. |
What will be uncertainty in the density of a cube if uncertainty in mass and length is 2% and 3% respectively? |
| Answer» SOLUTION :`PM 11%` | |
| 13174. |
A body is allowed to fall from a heigh h above the ground. Then match the following {:(,"List - I",,"List - II"),((a),PE=KE,(e ),"at height h/2"),((b),PE=2KE,(f),"constant at any point"),((c ),KE=2PE,(g),"at height 2h/3"),((d),PE+KE,(h),"at height h/3"):} |
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Answer» a-e, b-g, c-h, d-f |
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| 13175. |
A cylinder with a movable piston contains 3 moles of hydrogen at standard temperature and pressure. The walls of the cylinder are made of a heat insulator, and the piston is insulated by having a pile of sand on it. By what factor does the pressure of the gas increase if the gas is compressed to half its original volume ? |
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Answer» 2.64 |
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| 13176. |
A rod of length l is held vertically stationary with its lower end located at a point 'P', on the horizontal plane. When the rod is released to topple about 'P', the velocity of the upper end of the rod with which it hits the ground is |
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Answer» `SQRT((G)/(L))` |
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| 13177. |
If the displacement (x) and velocity (v) of a particle executing S.H.M are related through the expression 4V^(2) = 25 -x^(2), then its time period is |
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Answer» PERIODIC but not SHM |
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| 13178. |
An object that is dropped freely from rest travels for 5 seconds. What is the distance travelled in the last 2 seconds of its journey. |
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| 13179. |
Explain the torque acting on a rigid body. |
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Answer» Solution :As shown in the figure a rigid body rotates about a FIXED axis OZ. `vec(F_(1)),vec(F_(2))….vec(F_(n))` are the forces acting on the particles with position vectors `vec(r_(1)),vec(r_(2)),vec(r_(3))…..vec(r_(n))`. Respectively. The force `vec(F)_(n)` is acting on the PARTICLE with position vector `vec(r_(n))`. The torque on it is given by, `vec(tau_(n))=vec(r_(n))xxvec(F)_(n)` `=|(hati,HATJ,hatk),(x_(n),y_(n),z_(n)),(F_(nx),F_(ny),F_(nz))|` `therefore vectau=hati[y_(n)F_(nz)-Z_(n)F_(ny)]+hatj[Z_(n)F_(nx)-x_(n)F_(nz)]+hatk[x_(n)F_(ny)-y_(n)F_(nx)]....(1)` The torque acting on the rigid body can be obtained by taking the vector sum of such torques. `therefore vectau=underset(n)sumhati[y_(n)F_(nz)-Z_(n)F_(ny)]+hatj[Z_(n)F_(nx)-x_(n)F_(nz)]+hatk[x_(n)F_(ny)-y_(n)F_(nx)]` The Z component of this torque is responsible for the torsional motion of the rigid body about Z-axis. Similarly X and Y components of torque are responsible for the motion about X and Y axis respectively. In GENERAL if rotational motion is about a fixed axis with `hatn` as the unit vector on it, the component of the torque responsible for rotational motion is `vectau.hatn`. In the rotational motion of a rigid body it is not necessary to apply forces on all the particles of the body. Since the relative positions of the particles of a rigid body are invariant, a torque appliedon any particle can be considered to be the torque on the entire body. So if `vecF` is a force on a particle and `vecr` is the position vector of the particle the torque on the body can be taken as. `vectau=vecrxxvecF` |
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| 13180. |
A car is moving along a straight line, say OP in Fig. It moves from O to P in 18 s and returns from P to Q in 6.0 s. What are the average velocity and average speed of the car in going (a) from O to P ? and (b) from O to P and back to Q ? |
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Answer» Solution :(a)AVERAGE velocity = `("Displacement")/("TIME internal")` `bar(upsilon)=(+360m)/(18S)=+20 ms^(-1)` Average speed `=("Path length")/("Time interval")` `=(360m)/(18s)=20 ms^(-1)` Thus, in this case the average speed is equal to the magnitude of the average velocity. (b) In this case, Average velocity `=("Displacement")/("Time interval")=(+240m)/((18+6.0)s)` `=+10 ms^(-1)` Average speed `=("Path length")/("Time interval")=(OP+PQ)/(Delta t)` `=((360+120)m)/(24s)=20 ms^(-1)` Thus, in this case the average speed is not equal to the magnitude of the average velocity. This happens because the motion here involves change in direction so that the path length is greater than the magnitude of displacement. This shows that speed is, in general, greater than the magnitude of the velocity. |
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| 13181. |
State whether the viscosity of a gas increases or decrease due to an increase in temperature. |
| Answer» SOLUTION :INCREASES | |
| 13182. |
There are four vernierscales, whose observations are given in column - I and the correcponding calculations of least count are given in column - II. Match column - I with column - II appropriately. (Here S = value of IMSD : N = Value of number of divisions on vernier) (Assume ideal conditions){:(,"Column - I",,"Column - II"),((A),S=1mm : N=10,(P),0.05 mm),((B),S=0.5mm : N=10,(Q),0.01mm),((C ),S=0.5 mm : N=20,(R ),0.1 mm),((D),S=1mm : N=100,(S),0.025 mm):} |
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| 13183. |
A person wear glasses of power -2.5D. The defect of the eye and far point of the person without glasses are respectively. |
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Answer» farsightness 40cm |
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| 13184. |
A person carrying a box on his head is walking on a level road from one place to naother on a straight road is doing no work . The statement is …………. |
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Answer» partlycorrect INCORRECT |
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| 13185. |
A closed cubical box is made of a perfectly insulating material walls of thickness 8cm and the only way for heat to enter or leave the box is through two solid metallic cylindrical plugs, each of cross-sectional area 12cm^(2) and length 8cm, fixed in the opposite walls of the box. The outer surface A on one plug is maintained at 100^(@)C while the outer surface B of the other plug is maintained at 4^(@)C. The thermal conductivity of the material of each plug is 0.5 cal//.^(@)C//cm. A source of energy generating 36 cal//s is enclosed inside the box. Assuming the temperature to be the same at all points on the inner surface, the equilibrium temperature of the inner surface of the box is |
| Answer» Answer :C | |
| 13186. |
Centre of mass and centre of gravity of a body are not the same in general __ correct or incorrect ? |
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| 13187. |
A thermodynamic system undergoes cyclic process ABCDA as shown in figure. The work done by the system in the cycle is |
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Answer» `P_(0)V_(0)` As is CLEAR from figure, `W_(AEDA) = + "area of " DELTA AED = + (1)/(2)P_(0)V_(0)` `W_(BCEB) = -"Area of "Delta BCE = -(1)/(2)P_(0)V_(0)` The net work done by the system is `W_("net") = W_(AEDA) + W_(BCEB) = + (1)/(2)P_(0)V_(0) - (1)/(2)P_(0)V_(0)` = zero 
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| 13188. |
What are the limitations of the first law of thermodynamics? |
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Answer» Solution :Limitations of first law of THERMODYNAMICS: The first law of thermodynamics explains well the inter convertibility of heat and work. But it does not indicate the direction of CHANGE. For example, (a) When a hot object is in contact with a cold object, heat always flows from the hot object to cold object but not in the reverse direction. According to first law, it is POSSIBLE for the energy to flow from hot object to cold object or from cold object to hot object. But in nature the direction of heat flow is always from higher temperature to lower temperature. (B) When brakes are applied, a car stops due to friction and the work done against friction is converted into heat. But this heat is not reconverted to the kinetic energy of the car. So the first law is not sufficient to explain many of natural phenomena. |
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| 13189. |
A particle execute SHM between amplitude +A and -A. Find the position +x of particle such that time taken by it from zero to +x and to go from +x to +A is same: |
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Answer» `A/2` |
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| 13190. |
When a solid sphere is rolling along level surface the percentage of its total energy that is translational is |
| Answer» ANSWER :B | |
| 13191. |
Match List - I with List - II {:("List-I","List-II"),("(A) Ratio of angular velocities of hours hand of a clock and self rotation of the earth","(P) 12:1"),("(B) Ratio of angular velocities of seconds hand to minutes hand of a clock","(Q) 60:1"),("(C) Ratio of angular velocities of seconds hand to hours hand of a clock","(R) 2:1"),("(D) Ratio of angular velocities velocities of minutes hand to hours hand of a clock","(S) 720:1"):} |
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| 13192. |
In Column-I processes and in Column-II formulas of work are given. Match them appropriately : |
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| 13193. |
If the resultant external force on a system is zero, then the total…………of system remains constant. |
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Answer» Linear momentum `THEREFORE p` = constant `therefore MV` = constant, m is constant `therefore v` = constant |
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| 13194. |
Two bodies A and B have emissivities of 0.01 and 0.81 respectively. The outer surface areas of the two bodies are the same. The two bodies radiate energy at the same rate. The wavelength l, corresponding to the maximum spectral radiant power in the radiation from B, is shifted from the wavelength corresponding to the maximum spectral radiant power in the radiation from A by 10^(-6)m. If the temperature of A is 5802 K. Find the temperature of body B |
| Answer» Answer :B | |
| 13195. |
Two bodies A and B have emissivities of 0.01 and 0.81 respectively. The outer surface areas of the two bodies are the same. The two bodies radiate energy at the same rate. The wavelength l, corresponding to the maximum spectral radiant power in the radiation from B, is shifted from the wavelength corresponding to the maximum spectral radiant power in the radiation from A by 10^(-6)m. If the temperature of A is 5802 K. Find the wavelength of the radiation emitted from body B corresponding to maximum spectral radiant power. |
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Answer» `10^(-6)` m |
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| 13196. |
(A) : The centre of mass of uniform triangular lamina is centroid. (R ): Centroid is centre of symmetry of mass of the triangular lamina. |
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Answer» Both 'A' and 'R' and TRUE and 'R' is the CORRECT EXPLANTATION of 'A' |
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| 13197. |
The time interval between two successive noon when sun passes through zenith point ( meridian ) is known as |
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Answer» SIDEREAL day |
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| 13198. |
A disc of mass M and radius R moves in the x-y plane as shown in the fig. The angular momentum of the disc at the instant shown is : |
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Answer» `3/2mR^(2)OMEGA` about O |
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| 13199. |
A man is standing on a spring platform Reading of spring balance is 60 Kg. wt. If man jumps outside platform, then reading of the spring balance |
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Answer» FIRST INCREASE and then DECREASES to ZERO |
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| 13200. |
A body P is thrown vertically up with velocity 30 ms^(-1) and another body Q is thrown up along the same vertically line with the same velocity but 1 second later from the ground. When they meet (g=10ms^(-2)). |
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Answer» <P>P TRAVELS for 2.5s |
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