50278 + Interview Questions in Physics

1.	A 50 cm string fixed at both ends produces resonant frequency 384 Hz and 288 Hz without there being any other resonant frequency between the two. Find the speed of the wave on the string in cm/sec.
Answer» A $50 cm$ string fixed at both ends produces resonant frequency $384 Hz$ and $288 Hz$ without there being any other resonant frequency between the two. Find the speed of the wave on the string in $cm/sec$ .

Discussion

2.	Two rods of different materials with coefficients of thermal conductivity 'alpha 1' and 'alpha 2' ; Young's modulii Y1 and Y2 respectively; of initial lengths l1 and l2 respectively of equal cross-sectional areas are joined end at one end.The free ends are fixed to two vertical walls. Tenperature of the surrounding is then increased by T°C. Find out the displacement of the joint of the rods.
Answer» Two rods of different materials with coefficients of thermal conductivity 'alpha 1' and 'alpha 2' ; Young's modulii Y₁ and Y₂ respectively; of initial lengths l₁and l₂respectively of equal cross-sectional areas are joined end at one end.The free ends are fixed to two vertical walls. Tenperature of the surrounding is then increased by T°C. Find out the displacement of the joint of the rods.

Discussion

3.	In young's double slit experiment, the two slits act as coherent sources of equal amplitude A and of wavelength λ. In another experiment with the same set up, the two slits are sources of equal amplitude A and wavelength λ but are incoherent. The ratio of the intensity of light at the midpoint of the screen in the first case of that in the second case is
Answer» In young's double slit experiment, the two slits act as coherent sources of equal amplitude A and of wavelength $λ .$ In another experiment with the same set up, the two slits are sources of equal amplitude A and wavelength $λ$ but are incoherent. The ratio of the intensity of light at the midpoint of the screen in the first case of that in the second case is

Discussion

4.	Speed of sound in air is found to be 344ms at 80∘ C. Find the change in speed of sound for a 1∘ C increase in temperature.
Answer» Speed of sound in air is found to be 344 $\frac{m}{s}$ at 80 $^{\circ}$ C. Find the change in speed of sound for a 1 $^{\circ}$ C increase in temperature.

Discussion

5.	A room has a window fitted with a single 1.0 m × 2.0 m glass of thickness 2 mm. (a) Calculate the rate of heat flow through the closed window when the temperature inside the room is 32∘C and that outside is 40∘C. (b) The glass is now replaced by two glasspanes, each having a thickness of 1 mm and separated by a distance of 1 mm. Calculate the rate of heat flow under the same cnditions of temperature. Thermal conductivity of window glass = 1.0Js−1m−1∘C−1 and that of air = 0.025Js−1m−1∘C−1.
Answer» A room has a window fitted with a single 1.0 m $\times$ 2.0 m glass of thickness 2 mm. (a) Calculate the rate of heat flow through the closed window when the temperature inside the room is $32^{\circ} C$ and that outside is $40^{\circ} C$ . (b) The glass is now replaced by two glasspanes, each having a thickness of 1 mm and separated by a distance of 1 mm. Calculate the rate of heat flow under the same cnditions of temperature. Thermal conductivity of window glass = $1.0 J s^{- 1} m^{- 1 \circ} C^{- 1}$ and that of air = $0.025 J s^{- 1} m^{- 1 \circ} C^{- 1}$ .

Discussion

6.	Under what conditions does a heat engine work as a refrigerator?
Answer» Under what conditions does a heat engine work as a refrigerator?

Discussion

7.	A moving coil galvanometer is converted into an ammeter reading upto 0.03 A by connecting a shunt of resistance 4r across it and into an ammeter reading upto 0.06 A when a shunt of resistance r connected across it. What is the maximum current which can be sent through this galvanometer if no shunt is used.
Answer» A moving coil galvanometer is converted into an ammeter reading upto 0.03 A by connecting a shunt of resistance 4r across it and into an ammeter reading upto 0.06 A when a shunt of resistance r connected across it. What is the maximum current which can be sent through this galvanometer if no shunt is used.

Discussion

8.	A stone of mass of 16 kg is attached to a string 144 m long and is whirled in a horizontal circle. The maximum tension the string can withstand is 16 Newton. The maximum velocity of revolution that can be given to the stone without breaking it, will be
Answer» A stone of mass of 16 kg is attached to a string 144 m long and is whirled in a horizontal circle. The maximum tension the string can withstand is 16 Newton. The maximum velocity of revolution that can be given to the stone without breaking it, will be

Discussion

9.	An elevator without a ceiling is ascending up with an acceleration of 5 ms−2. A boy on the elevator shoots a ball in vertical upward direction from a height of 2 m above the floor of elevator. At this instant the elevator is moving up with a velocity of 10 ms−1, and the floor of the elevator is at a height of 50 m from the ground. The initial speed of the ball is 15 ms−1 with respect to the elevator. Consider the duration for which the ball strikes the floor of elevator in answering following questions. (g=10 ms−2)
Answer» An elevator without a ceiling is ascending up with an acceleration of $5 {ms}^{- 2}$ . A boy on the elevator shoots a ball in vertical upward direction from a height of $2 m$ above the floor of elevator. At this instant the elevator is moving up with a velocity of $10 {ms}^{- 1}$ , and the floor of the elevator is at a height of $50 m$ from the ground. The initial speed of the ball is $15 {ms}^{- 1}$ with respect to the elevator. Consider the duration for which the ball strikes the floor of elevator in answering following questions. ( $g = 10 {ms}^{- 2}$ )

Discussion

10.	A screw gauge has a pitch of 1 mm and there are 100 divisions on the circular scale. The instrument reads +2 divisions when nothing is put in between its jaws. In measuring the thickness of a metal sheet, there are 8 divisions on the main scale and 83rd division coincides with the reference line. What is the thickness of the sheet?
Answer» A screw gauge has a pitch of 1 mm and there are 100 divisions on the circular scale. The instrument reads +2 divisions when nothing is put in between its jaws. In measuring the thickness of a metal sheet, there are 8 divisions on the main scale and $83^{r d}$ division coincides with the reference line. What is the thickness of the sheet?

Discussion

11.	A ball of mass 5 kg is thrown towards the floor making an angle 60° with the vertical with velocity 10 m/s. calculate the Impulse during the time period when the ball was in contact with the surface
Answer» A ball of mass 5 kg is thrown towards the floor making an angle 60° with the vertical with velocity 10 m/s. calculate the Impulse during the time period when the ball was in contact with the surface

11.

A ball of mass 5 kg is thrown towards the floor making an angle 60° with the vertical with velocity 10 m/s. calculate the Impulse during the time period when the ball was in contact with the surface

Answer»

A ball of mass 5 kg is thrown towards the floor making an angle 60° with the vertical with velocity 10 m/s. calculate the Impulse during the time period when the ball was in contact with the surface

Discussion

12.	A bullet of mass 2gm is having a charge of 2 micro coulomb .Through what potential difference must it be accelerated starting from rest to acquire a speed of 10 m/s
Answer» A bullet of mass 2gm is having a charge of 2 micro coulomb .Through what potential difference must it be accelerated starting from rest to acquire a speed of 10 m/s

Discussion

13.	A battery is used to charge a parallel plate capacitor till it becomes fully charged. If capacitance is C and EMF of battery is ∈, find average current from t=0 to t=RC. (R = resistance of circuit)
Answer» A battery is used to charge a parallel plate capacitor till it becomes fully charged. If capacitance is $C$ and EMF of battery is $\in$ , find average current from $t = 0$ to $t = R C$ . ( $R$ = resistance of circuit)

Discussion

14.	For one mole of a van der Waals gas for which b=0 and T=300 K, the PV vs 1V plot is shown below. The value of the van der Waals constant a (in atm L mol−2) is:
Answer» For one mole of a van der Waals gas for which $b = 0$ and $T = 300 K$ , the $P V vs \frac{1}{V}$ plot is shown below. The value of the van der Waals constant $a$ (in ${atm L mol}^{- 2}$ ) is:

Discussion

15.	From a height of 5m a ball is thrown vertically downwards with an initial velocity of 10m/s towards a hard horizontal floor. If it bounces to the same height the coefficient of restitution is (g=10ms−2)
Answer» From a height of 5m a ball is thrown vertically downwards with an initial velocity of 10m/s towards a hard horizontal floor. If it bounces to the same height the coefficient of restitution is $(g = 10 m s^{- 2})$

Discussion

16.	A uniform thin bar of mass 6m and length 12L is bent to make an regular hexagon. Its moment of inertia about an axis passing through the centre of mass and perpendicular to the plane of hexagon is :
Answer» A uniform thin bar of mass $6 m$ and length $12 L$ is bent to make an regular hexagon. Its moment of inertia about an axis passing through the centre of mass and perpendicular to the plane of hexagon is :

Discussion

17.	An arc lamp requires a direct current of 10 A at 80 V to function. If it is connected to a 220 V (rms), 50Hz AC supply, the series inductor needed for it to work is close to:
Answer» An arc lamp requires a direct current of 10 A at 80 V to function. If it is connected to a 220 V (rms), 50Hz AC supply, the series inductor needed for it to work is close to:

Discussion

18.	A particle which is constrained to move along the x-axis, is subjected to a force in the same direction which varies with the distance x of the particle from the origin as F(x)=−kx+ax3. Here k and a are positive constants. For x≥0, the functional from of the potential energy U(x) of the particle is
Answer» A particle which is constrained to move along the x-axis, is subjected to a force in the same direction which varies with the distance x of the particle from the origin as $F (x) = - k x + a x^{3}$ . Here k and a are positive constants. For $x \geq 0$ , the functional from of the potential energy $U_{(x)}$ of the particle is

Discussion

19.	A T.V. transmission tower at a particular station has height 160 m, earth's radius is 6400 km. What is population covered, if population density is 1200/km2 ?
Answer» A T.V. transmission tower at a particular station has height $160 m$ , earth's radius is $6400 km$ . What is population covered, if population density is $1200 {/km}^{2}$ ?

Discussion

20.	Circular loop of a wire and a long straight wire carry current Ic and Ie respectively as shown in figure. Assuming that these are placed in the same plane. The magnetic field will be zero at the centre of the loop when the separation H is:
Answer» Circular loop of a wire and a long straight wire carry current Ic and Ie respectively as shown in figure. Assuming that these are placed in the same plane. The magnetic field will be zero at the centre of the loop when the separation H is:

20.

Circular loop of a wire and a long straight wire carry current Ic and Ie respectively as shown in figure. Assuming that these are placed in the same plane. The magnetic field will be zero at the centre of the loop when the separation H is:

Answer»

Circular loop of a wire and a long straight wire carry current Ic and Ie respectively as shown in figure. Assuming that these are placed in the same plane. The magnetic field will be zero at the centre of the loop when the separation H is:

Discussion

21.	In a uniform gravitational field g, which is acting vertically downward, a ball is thrown at an angle with horizontal such that the initial (immediately after projection) radius of curvature is 8 times the minimum radius of curvature. If angle of projection is 150o , then find the value of θ
Answer» In a uniform gravitational field g, which is acting vertically downward, a ball is thrown at an angle with horizontal such that the initial (immediately after projection) radius of curvature is 8 times the minimum radius of curvature. If angle of projection is $150^{o}$ , then find the value of $θ$

Discussion

22.	A horizontally oriented tube AB of length 'l' rotates with a constant angular velocity ′ω′ about a stationary vertical axis O1O2 passing through the end A as shown in the figure. The tube is filled with an ideal fluid. The end A of the tube is open. [Consider P0=Patm ] If end B is closed, the pressure just inside the tube at B as a function of the length of liquid column ‘h’ is
Answer» A horizontally oriented tube AB of length 'l' rotates with a constant angular velocity $^{'} ω^{'}$ about a stationary vertical axis $O_{1} O_{2}$ passing through the end A as shown in the figure. The tube is filled with an ideal fluid. The end A of the tube is open. [Consider $P_{0} = P_{a t m}$ ] If end B is closed, the pressure just inside the tube at B as a function of the length of liquid column ‘h’ is

Discussion

23.	A launching pad with a spaceship is moving along a circular orbit of the moon, whose radius R is triple that of the moon Rm. The ship leaves the launching pad with a relative velocity equal to the launching pad's initial orbital velocity V0 and the launching pad then falls to the moon. If the angle θ=cos−1 n√10 with the horizontal is the angle at which the launching pad crashes into the surface and its mass is twice that of the spaceship, then the value of n is
Answer» A launching pad with a spaceship is moving along a circular orbit of the moon, whose radius $R$ is triple that of the moon $R_{m}$ . The ship leaves the launching pad with a relative velocity equal to the launching pad's initial orbital velocity $V_{0}$ and the launching pad then falls to the moon. If the angle $θ = c o s^{- 1} \frac{n}{\sqrt{10}}$ with the horizontal is the angle at which the launching pad crashes into the surface and its mass is twice that of the spaceship, then the value of $n$ is

Discussion

24.	Consider the circuit shown below where all resistors are of 1 k ΩIf a current of magnitude 1 mA flows through the resistor marked X, what is the potential difference measured between point P and Q?
Answer» Consider the circuit shown below where all resistors are of 1 k $Ω$ If a current of magnitude 1 mA flows through the resistor marked X, what is the potential difference measured between point P and Q?

24.

Consider the circuit shown below where all resistors are of 1 k ΩIf a current of magnitude 1 mA flows through the resistor marked X, what is the potential difference measured between point P and Q?

Answer»

Consider the circuit shown below where all resistors are of 1 k $Ω$

If a current of magnitude 1 mA flows through the resistor marked X, what is the potential difference measured between point P and Q?

Discussion

25.	Calculate the area of the triangle determined by the two vectors →A=3^i+4^j and →B=−3^i+7^j.
Answer» Calculate the area of the triangle determined by the two vectors $\to A = 3^i + 4^j a n d \to B = - 3^i + 7^j .$

Discussion

26.	A hydrogen like gas atoms absorb radiations of wavelength λ0 and consequently emit radiations of 6 different wavelengths of which, two wavelengths are shorter than λ0. Choose the correct alternative(s).
Answer» A hydrogen like gas atoms absorb radiations of wavelength $λ_{0}$ and consequently emit radiations of 6 different wavelengths of which, two wavelengths are shorter than $λ_{0}$ . Choose the correct alternative(s).

Discussion

27.	Two ladies were asked to rank ten different types of cell phones. The ranks given by them are given below: Cell PhoneABCDEFGHIJTina16395271084Rita68372159410 Calculate Spearman's rank correlation coefficient.
Answer» Two ladies were asked to rank ten different types of cell phones. The ranks given by them are given below: $\begin{matrix} Cell Phone & A & B & C & D & E & F & G & H & I & J Tina & 1 & 6 & 3 & 9 & 5 & 2 & 7 & 10 & 8 & 4 Rita & 6 & 8 & 3 & 7 & 2 & 1 & 5 & 9 & 4 & 10 \end{matrix}$ Calculate Spearman's rank correlation coefficient.

27.

Two ladies were asked to rank ten different types of cell phones. The ranks given by them are given below: Cell PhoneABCDEFGHIJTina16395271084Rita68372159410 Calculate Spearman's rank correlation coefficient.

Answer»

Two ladies were asked to rank ten different types of cell phones. The ranks given by them are given below:

$\begin{matrix} Cell Phone & A & B & C & D & E & F & G & H & I & J Tina & 1 & 6 & 3 & 9 & 5 & 2 & 7 & 10 & 8 & 4 Rita & 6 & 8 & 3 & 7 & 2 & 1 & 5 & 9 & 4 & 10 \end{matrix}$

Calculate Spearman's rank correlation coefficient.

Discussion

28.	The kinetic energy of a body is increased by 21%. What is the percentage increase in the magnitude of linear momentum of the body?
Answer» The kinetic energy of a body is increased by $21 %$ . What is the percentage increase in the magnitude of linear momentum of the body?

28.

The kinetic energy of a body is increased by 21%. What is the percentage increase in the magnitude of linear momentum of the body?

Answer»

The kinetic energy of a body is increased by $21 %$ . What is the percentage increase in the magnitude of linear momentum of the body?

Discussion

29.	Two satellites S1 and S2 revolve round a planet in coplanar circular orbits in the same sense. Their periods of revolution are 1 hour and 8 hours respectively. The radius of the orbit of S1 is 104 km. When S2 is closest to S1, angular speed (in rad/hr) of S2 as observed by an astronaut in S1 is
Answer» Two satellites $S_{1}$ and $S_{2}$ revolve round a planet in coplanar circular orbits in the same sense. Their periods of revolution are 1 hour and 8 hours respectively. The radius of the orbit of $S_{1}$ is $10^{4} km$ . When $S_{2}$ is closest to $S_{1}$ , angular speed (in $r a d / h r$ ) of $S_{2}$ as observed by an astronaut in $S_{1}$ is

Discussion

30.	π/4∫0sinx.cosx dx=
Answer» $π / 4 \int 0 sin x . cos x d x =$

Discussion

31.	A wire is bent at an angle θ. A rod of mass m can slide along the bent wire without friction as shown in the figure. A soap film is maintained in the wire frame kept in a vertical position and the rod is in equilibrium as shown in the figure. If rod is displaced slightly in vertical direction, then the time period of small oscillations of the rod is :-
Answer» A wire is bent at an angle $θ$ . A rod of mass $m$ can slide along the bent wire without friction as shown in the figure. A soap film is maintained in the wire frame kept in a vertical position and the rod is in equilibrium as shown in the figure. If rod is displaced slightly in vertical direction, then the time period of small oscillations of the rod is :-

Discussion

32.	The Kα X-ray of molybdenum has wavelength 71 pm. If the energy of a molybdenum atom with a K electron knocked out is 23.32 keV, What will be the energy of this atom when an L electron is knocked out?
Answer» The $K_{α}$ X-ray of molybdenum has wavelength 71 pm. If the energy of a molybdenum atom with a K electron knocked out is 23.32 keV, What will be the energy of this atom when an L electron is knocked out?

Discussion

33.	In the pulley system shown, if radii of the bigger and smaller pulley are 2m and 1m respectively and acceleration of block A is 5 m/s2 then the acceleration of block B will be:
Answer» In the pulley system shown, if radii of the bigger and smaller pulley are 2m and 1m respectively and acceleration of block A is $5 m / s^{2}$ then the acceleration of block B will be:

33.

In the pulley system shown, if radii of the bigger and smaller pulley are 2m and 1m respectively and acceleration of block A is 5 m/s2 then the acceleration of block B will be:

Answer»

In the pulley system shown, if radii of the bigger and smaller pulley are 2m and 1m respectively and acceleration of block A is $5 m / s^{2}$ then the acceleration of block B will be:

Discussion

34.	If a capacitor of 10μF is charged to 10V and then connected to a new circuit to discharge through a10Ω resistor, the charge on it after 20μs is.
Answer» If a capacitor of $10 μ F$ is charged to 10V and then connected to a new circuit to discharge through a $10 Ω$ resistor, the charge on it after $20 μ s$ is.

Discussion

35.	A force F is applied on a block of mass 75 kg at an angle of 53∘ with the horizontal. If the coefficient of friction between the floor and the block is 0.6, then what is the maximum value of force F that can be applied before the block starts moving?
Answer» A force $F$ is applied on a block of mass $75 kg$ at an angle of $53^{\circ}$ with the horizontal. If the coefficient of friction between the floor and the block is $0.6$ , then what is the maximum value of force $F$ that can be applied before the block starts moving?

Discussion

36.	Three forces act on a body and the body stays at equilibrium. The direction of the two forces are shown in the figure. The direction of the third force to keep the body in equilibrium is (Given F1=F2)
Answer» Three forces act on a body and the body stays at equilibrium. The direction of the two forces are shown in the figure. The direction of the third force to keep the body in equilibrium is (Given $F_{1} = F_{2}$ )

Discussion

37.	Consider the triangle having vertices O(0,0),A(4,0) and B(2,2√3). Let P be an interior point inside ΔOAB. and R be the region consisting of all those points P which satisfy OP≤min[BP,AP]. Let the area of the region R is α. Then the value of 4√3α is
Answer» Consider the triangle having vertices $O (0, 0), A (4, 0)$ and $B (2, 2 \sqrt{3})$ . Let $P$ be an interior point inside $Δ O A B .$ and $R$ be the region consisting of all those points $P$ which satisfy $O P \leq min [B P, A P]$ . Let the area of the region $R$ is $α$ . Then the value of $4 \sqrt{3} α$ is

Discussion

38.	A rectangular film of liquid is extended from (2 cm×8 cm) to (4 cm×16 cm). If work done is 5 ×10−4 J, value of the surface tension of the liquid is
Answer» A rectangular film of liquid is extended from $(2 cm \times 8 cm)$ to $(4 cm \times 16 cm)$ . If work done is $5 \times 10^{- 4} J$ , value of the surface tension of the liquid is

Discussion

39.	Immediately on cutting the taut string, the acceleration of one of the blocks is found to be 2 ms−2. If m1=6 kg,m2 is equal to (g=10 ms−2)
Answer» Immediately on cutting the taut string, the acceleration of one of the blocks is found to be $2 m s^{- 2} .$ If $m_{1} = 6 k g, m_{2}$ is equal to $(g = 10 m s^{- 2})$

Discussion

40.	A parallel plate capacitor with plates of width 4 cm, length 10 cm and separation between plates is 4 cm, is connected across a battery of emf 12 Volt. A dielectric slab of dielectric constant K=7 is slowly introduced between the plates. Force exerted on dielectric slab by the field is
Answer» A parallel plate capacitor with plates of width $4$ cm, length $10$ cm and separation between plates is $4$ cm, is connected across a battery of emf $12$ Volt. A dielectric slab of dielectric constant $K = 7$ is slowly introduced between the plates. Force exerted on dielectric slab by the field is

Discussion

41.	A double slit is illuminated by light of wavelength 6000 ∘A. The slits are 0.1 cm apart and the screen is placed one meter away. Then the angular position of the 10th maximum in radian and separation of the two adjacent minima will be respectively
Answer» A double slit is illuminated by light of wavelength $6000 \circ A$ . The slits are $0.1 c m$ apart and the screen is placed one meter away. Then the angular position of the $10^{t h}$ maximum in radian and separation of the two adjacent minima will be respectively

Discussion

42.	The bob of a pendulum at rest is given a sharp hit to impart a horizontal velocity u=√10gl, where l is the length of the pendulum. Find the velocity of the bob when the string is horizontal.
Answer» The bob of a pendulum at rest is given a sharp hit to impart a horizontal velocity $u = \sqrt{10 g l}$ , where $l$ is the length of the pendulum. Find the velocity of the bob when the string is horizontal.

Discussion

43.	The position coordinates of a projectile projected from ground on a certain planet (with no atmosphere) are given by y=(4t−2t2) m and x=(3t) m, where t is in seconds and point of projection is taken as origin. The angle of projection of projectile with vertical is
Answer» The position coordinates of a projectile projected from ground on a certain planet (with no atmosphere) are given by $y = (4 t - 2 t^{2}) m$ and $x = (3 t) m$ , where $t$ is in seconds and point of projection is taken as origin. The angle of projection of projectile with vertical is

Discussion

44.	A small block is connected to one end of two identical massless strings of length 1623 cm each with their other ends fixed to a vertical rod. If the ratio of tensions T1T2 is 4:1, then what will be the angular velocity of the block? [Take g=9.8 ms−2].
Answer» A small block is connected to one end of two identical massless strings of length $16 \frac{2}{3} cm$ each with their other ends fixed to a vertical rod. If the ratio of tensions $\frac{T_{1}}{T_{2}}$ is $4 : 1$ , then what will be the angular velocity of the block? [Take $g = 9.8 {ms}^{- 2}$ ].

Discussion

45.	Two cars are moving in the same direction with a speed of 30 kmph. They are seperated from each other by 5 km. Third car moving in the opposite direction meets the two cars after an interval of 4 minutes. What is the speed of the third car?
Answer» Two cars are moving in the same direction with a speed of $30 kmph$ . They are seperated from each other by $5 km$ . Third car moving in the opposite direction meets the two cars after an interval of 4 minutes. What is the speed of the third car?

Discussion

46.	Find the distance of COM of a solid hemisphere of radius 16 cm from its geometric centre.
Answer» Find the distance of $COM$ of a solid hemisphere of radius $16 cm$ from its geometric centre.

Discussion

47.	Answer to question, ID is 453019 key answer is option d -- 20/3
Answer» Answer to question, ID is 453019 key answer is option d -- 20/3

Discussion

48.	Three equal objects of mass M each are placed on a table at points (0,0),(6,0) and (0,6) respectively . If another object of mass 2M is placed at point (2,7), the displacement of COM is
Answer» Three equal objects of mass $M$ each are placed on a table at points $(0, 0), (6, 0)$ and $(0, 6)$ respectively . If another object of mass $2 M$ is placed at point $(2, 7)$ , the displacement of $C O M$ is

Discussion

49.	A 100 m long train crosses a man travelling at 5 km/h in the opposite direction in 7.2 s. Then the velocity of train is
Answer» A $100 m$ long train crosses a man travelling at $5 km/h$ in the opposite direction in $7.2 s$ . Then the velocity of train is

Discussion

50.	A body of mass 1 kg begins to move under the action of a time dependent force →F=(2t^i+3t2^j) N. Calculate the instantaneous power developed at time t ?
Answer» A body of mass $1 kg$ begins to move under the action of a time dependent force $\to F = (2 t^i + 3 t^{2}^j) N$ . Calculate the instantaneous power developed at time $t$ ?

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

A 50 cm string fixed at both ends produces resonant frequency 384 Hz and 288 Hz without there being any other resonant frequency between the two. Find the speed of the wave on the string in cm/sec.

Speed of sound in air is found to be 344ms at 80∘ C. Find the change in speed of sound for a 1∘ C increase in temperature.

Under what conditions does a heat engine work as a refrigerator?

A stone of mass of 16 kg is attached to a string 144 m long and is whirled in a horizontal circle. The maximum tension the string can withstand is 16 Newton. The maximum velocity of revolution that can be given to the stone without breaking it, will be

A ball of mass 5 kg is thrown towards the floor making an angle 60° with the vertical with velocity 10 m/s. calculate the Impulse during the time period when the ball was in contact with the surface

A bullet of mass 2gm is having a charge of 2 micro coulomb .Through what potential difference must it be accelerated starting from rest to acquire a speed of 10 m/s

A battery is used to charge a parallel plate capacitor till it becomes fully charged. If capacitance is C and EMF of battery is ∈, find average current from t=0 to t=RC. (R = resistance of circuit)

For one mole of a van der Waals gas for which b=0 and T=300 K, the PV vs 1V plot is shown below. The value of the van der Waals constant a (in atm L mol−2) is:

From a height of 5m a ball is thrown vertically downwards with an initial velocity of 10m/s towards a hard horizontal floor. If it bounces to the same height the coefficient of restitution is (g=10ms−2)

A uniform thin bar of mass 6m and length 12L is bent to make an regular hexagon. Its moment of inertia about an axis passing through the centre of mass and perpendicular to the plane of hexagon is :

An arc lamp requires a direct current of 10 A at 80 V to function. If it is connected to a 220 V (rms), 50Hz AC supply, the series inductor needed for it to work is close to:

A T.V. transmission tower at a particular station has height 160 m, earth's radius is 6400 km. What is population covered, if population density is 1200/km2 ?

Circular loop of a wire and a long straight wire carry current Ic and Ie respectively as shown in figure. Assuming that these are placed in the same plane. The magnetic field will be zero at the centre of the loop when the separation H is:

In a uniform gravitational field g, which is acting vertically downward, a ball is thrown at an angle with horizontal such that the initial (immediately after projection) radius of curvature is 8 times the minimum radius of curvature. If angle of projection is 150o , then find the value of θ

Consider the circuit shown below where all resistors are of 1 k ΩIf a current of magnitude 1 mA flows through the resistor marked X, what is the potential difference measured between point P and Q?

Calculate the area of the triangle determined by the two vectors →A=3^i+4^j and →B=−3^i+7^j.

A hydrogen like gas atoms absorb radiations of wavelength λ0 and consequently emit radiations of 6 different wavelengths of which, two wavelengths are shorter than λ0. Choose the correct alternative(s).

Two ladies were asked to rank ten different types of cell phones. The ranks given by them are given below: Cell PhoneABCDEFGHIJTina16395271084Rita68372159410 Calculate Spearman's rank correlation coefficient.

The kinetic energy of a body is increased by 21%. What is the percentage increase in the magnitude of linear momentum of the body?

Two satellites S1 and S2 revolve round a planet in coplanar circular orbits in the same sense. Their periods of revolution are 1 hour and 8 hours respectively. The radius of the orbit of S1 is 104 km. When S2 is closest to S1, angular speed (in rad/hr) of S2 as observed by an astronaut in S1 is

π/4∫0sinx.cosx dx=

The Kα X-ray of molybdenum has wavelength 71 pm. If the energy of a molybdenum atom with a K electron knocked out is 23.32 keV, What will be the energy of this atom when an L electron is knocked out?

In the pulley system shown, if radii of the bigger and smaller pulley are 2m and 1m respectively and acceleration of block A is 5 m/s2 then the acceleration of block B will be:

If a capacitor of 10μF is charged to 10V and then connected to a new circuit to discharge through a10Ω resistor, the charge on it after 20μs is.

A force F is applied on a block of mass 75 kg at an angle of 53∘ with the horizontal. If the coefficient of friction between the floor and the block is 0.6, then what is the maximum value of force F that can be applied before the block starts moving?

Three forces act on a body and the body stays at equilibrium. The direction of the two forces are shown in the figure. The direction of the third force to keep the body in equilibrium is (Given F1=F2)

Consider the triangle having vertices O(0,0),A(4,0) and B(2,2√3). Let P be an interior point inside ΔOAB. and R be the region consisting of all those points P which satisfy OP≤min[BP,AP]. Let the area of the region R is α. Then the value of 4√3α is

A rectangular film of liquid is extended from (2 cm×8 cm) to (4 cm×16 cm). If work done is 5 ×10−4 J, value of the surface tension of the liquid is

Immediately on cutting the taut string, the acceleration of one of the blocks is found to be 2 ms−2. If m1=6 kg,m2 is equal to (g=10 ms−2)

A parallel plate capacitor with plates of width 4 cm, length 10 cm and separation between plates is 4 cm, is connected across a battery of emf 12 Volt. A dielectric slab of dielectric constant K=7 is slowly introduced between the plates. Force exerted on dielectric slab by the field is

A double slit is illuminated by light of wavelength 6000 ∘A. The slits are 0.1 cm apart and the screen is placed one meter away. Then the angular position of the 10th maximum in radian and separation of the two adjacent minima will be respectively

The bob of a pendulum at rest is given a sharp hit to impart a horizontal velocity u=√10gl, where l is the length of the pendulum. Find the velocity of the bob when the string is horizontal.

The position coordinates of a projectile projected from ground on a certain planet (with no atmosphere) are given by y=(4t−2t2) m and x=(3t) m, where t is in seconds and point of projection is taken as origin. The angle of projection of projectile with vertical is

A small block is connected to one end of two identical massless strings of length 1623 cm each with their other ends fixed to a vertical rod. If the ratio of tensions T1T2 is 4:1, then what will be the angular velocity of the block? [Take g=9.8 ms−2].

Two cars are moving in the same direction with a speed of 30 kmph. They are seperated from each other by 5 km. Third car moving in the opposite direction meets the two cars after an interval of 4 minutes. What is the speed of the third car?

Find the distance of COM of a solid hemisphere of radius 16 cm from its geometric centre.

Answer to question, ID is 453019 key answer is option d -- 20/3

Three equal objects of mass M each are placed on a table at points (0,0),(6,0) and (0,6) respectively . If another object of mass 2M is placed at point (2,7), the displacement of COM is

A 100 m long train crosses a man travelling at 5 km/h in the opposite direction in 7.2 s. Then the velocity of train is

A body of mass 1 kg begins to move under the action of a time dependent force →F=(2t^i+3t2^j) N. Calculate the instantaneous power developed at time t ?