50278 + Interview Questions in Physics Page 39 InterviewSolution

1901.	An express train is moving with a velocity v1. Its driver finds another train is moving on the same track in the same direction with velocity v2(v2<v1). To escape collision, driver applies a retardation a on the train. The minimum time to escape the collision is
Answer» An express train is moving with a velocity $v_{1}$ . Its driver finds another train is moving on the same track in the same direction with velocity $v_{2} (v_{2} < v_{1})$ . To escape collision, driver applies a retardation $a$ on the train. The minimum time to escape the collision is

Discussion

1902.	A force →F=6x^i+2y^j displaces a body from →r1=3^i+8^j to →r2=5^i−4^j. Find the work done by the force.
Answer» A force $\to F = 6 x^i + 2 y^j$ displaces a body from $_{1} = 3^i + 8^j$ to $_{2} = 5^i - 4^j$ . Find the work done by the force.

Discussion

1903.	The electric field in a certain region is given by, →E=(5^i) kV/m. The potential difference (VB−VA) between two points A and B having co-ordinates (4,0,0) and (10,3,0) respectively, is equal to -(co-ordinates x,y and z are in metre)
Answer» The electric field in a certain region is given by, $\to E = (5^i) kV/m$ . The potential difference $(V_{B} - V_{A})$ between two points $A$ and $B$ having co-ordinates $(4, 0, 0)$ and $(10, 3, 0)$ respectively, is equal to - $($ co-ordinates $x, y$ and $z$ are in metre $)$

Discussion

1904.	Find d²y/dx²:x=at²y=2at
Answer» Find d²y/dx²: x=at² y=2at

Discussion

1905.	A graph is plotted between magnitude of electric field (upon the y axis)and the distance upon the perpendicular bisector of long line charge(upon x axis).Draw the graph
Answer» A graph is plotted between magnitude of electric field (upon the y axis)and the distance upon the perpendicular bisector of long line charge(upon x axis).Draw the graph

Discussion

1906.	A soap film has been developed over a wire loop. If surface tension of the soap solution is 0.015 N/m, find the tension in the thread loop of length 12.56 cm which is kept over the soap film, when the soap film inside it is pricked.
Answer» A soap film has been developed over a wire loop. If surface tension of the soap solution is $0.015 N/m$ , find the tension in the thread loop of length $12.56 cm$ which is kept over the soap film, when the soap film inside it is pricked.

Discussion

1907.	The average kinetic energy of one mole of gas per degree of freedom (on the basis of theory of gases)
Answer» The average kinetic energy of one $mole$ of gas per degree of freedom (on the basis of theory of gases)

Discussion

1908.	An electron already accelerated through 100 V is further accelerated through an additional potential difference of 25 V.The fractional change in its de Broglie wavelength will be(approx)0.1050.2120.3330.452
Answer» An electron already accelerated through 100 V is further accelerated through an additional potential difference of 25 V.The fractional change in its de Broglie wavelength will be(approx) 0.105 0.212 0.333 0.452

Discussion

1909.	The kinetic energy of a projectile at its highest position is K. If the range of the projectile is 4 times the height of the projectile then find the initial kinetic energy of the projectile .
Answer» The kinetic energy of a projectile at its highest position is K. If the range of the projectile is 4 times the height of the projectile then find the initial kinetic energy of the projectile .

Discussion

1910.	A weight W is supported by two strings inclined at 60∘ and 30∘ to vertical. The tensions in the strings are T1 and T2 as shown. If these tensions have to be determined in terms of W using a triangle of forces, then which of the following triangles should be drawn ?(The blocks in equilibrium)
Answer» A weight $W$ is supported by two strings inclined at $60^{\circ}$ and $30^{\circ}$ to vertical. The tensions in the strings are $T_{1}$ and $T_{2}$ as shown. If these tensions have to be determined in terms of $W$ using a triangle of forces, then which of the following triangles should be drawn ? (The blocks in equilibrium)

Discussion

1911.	Curves of two waves propagating in the same medium is shown. Here, y is displacement in m and t is time in s. Find the ratio of their average intensities?
Answer» Curves of two waves propagating in the same medium is shown. Here, $y$ is displacement in $m$ and $t$ is time in $s$ . Find the ratio of their average intensities?

Discussion

1912.	A cell of constant emf first connected to a resistance R1 and then connected to a resistance R2. If power delivered in both cases is same, then the internal resistance of the cell is
Answer» A cell of constant emf first connected to a resistance $R_{1}$ and then connected to a resistance $R_{2}$ . If power delivered in both cases is same, then the internal resistance of the cell is

Discussion

1913.	Consider a hollow conducting cylinder with inner and outer radii 10 cm and 50 cm respectively and it carries a current I=9 A. Find the magnitude of magnetic induction at 30 cm from the axis of the cylinder.
Answer» Consider a hollow conducting cylinder with inner and outer radii $10 cm$ and $50 cm$ respectively and it carries a current $I = 9 A$ . Find the magnitude of magnetic induction at $30 cm$ from the axis of the cylinder.

Discussion

1914.	If converging line falls on concave lens then lines become parallel and if parallel lines fall on it then lines divergeIs this statement true??
Answer» If converging line falls on concave lens then lines become parallel and if parallel lines fall on it then lines diverge Is this statement true??

Discussion

1915.	Two travelling waves y = 0.10sin(3t +4πx) metres and y= 0.2sin(3t - 5πx) metres meet at t =0 what is the displacement at x=4.5 at this moment
Answer» Two travelling waves y = 0.10sin(3t +4πx) metres and y= 0.2sin(3t - 5πx) metres meet at t =0 what is the displacement at x=4.5 at this moment

Discussion

1916.	A post-tensioned concrete beam of 100 mm x 300 mm rectangular section is having cable with zero eccentricity at the supports and an eccentricity of 50 mm at the centre of span. The cross sectional area of the cable is 200mm2 and initial stress in the cable is 1200N/mm2, If the ultimate creep strain is 30×10−6 mm/mm per N/mm2 of stress and modulus of elasticity of steel is 210kN/mm2 then the loss of stress in steel only due to creep of concrete is______ N/mm2.62
Answer» A post-tensioned concrete beam of 100 mm x 300 mm rectangular section is having cable with zero eccentricity at the supports and an eccentricity of 50 mm at the centre of span. The cross sectional area of the cable is $200 m m^{2}$ and initial stress in the cable is $1200 N / m m^{2}$ , If the ultimate creep strain is $30 \times 10^{- 6}$ mm/mm per $N / m m^{2}$ of stress and modulus of elasticity of steel is $210 k N / m m^{2}$ then the loss of stress in steel only due to creep of concrete is______ $N / m m^{2}$ . 62

Discussion

1917.	Four metal plates numbered 1,2,3 and 4 are arranged as shown below. The area of each plate is A=10 cm2 and separation between adjacent plates is d=1.5 mm. The capacitance of the arrangement is
Answer» Four metal plates numbered $1, 2, 3$ and $4$ are arranged as shown below. The area of each plate is $A = 10 {cm}^{2}$ and separation between adjacent plates is $d = 1.5 mm$ . The capacitance of the arrangement is

Discussion

1918.	A point charge q is placed inside a conducting spherical shell of inner radius 2R and outer radius 3R at a distance of R from the centre of the shell. The electric potential at the centre of shell will be 14πϵ0 times.
Answer» A point charge q is placed inside a conducting spherical shell of inner radius 2R and outer radius 3R at a distance of R from the centre of the shell. The electric potential at the centre of shell will be $\frac{1}{4 π ϵ_{0}}$ times.

Discussion

1919.	Two air bubbles are joined to form a double bubble.If 3 cm and 4 cm are the individual radii of the two bubbles then the radius and the sense ofcurvature of the internal film surface common to both the bubbles is
Answer» Two air bubbles are joined to form a double bubble.If 3 cm and 4 cm are the individual radii of the two bubbles then the radius and the sense ofcurvature of the internal film surface common to both the bubbles is

Discussion

1920.	A car is moving on a plane inclined at 30∘ to the horizontal with an acceleration of 9.8 m/s2 parallel to the plane upward. A bob is suspended by a string from the roof. The angle in degrees which the string makes with the vertical is: (Assume that the bob does not move relative to car and g=9.8 m/s2)
Answer» A car is moving on a plane inclined at $30^{\circ}$ to the horizontal with an acceleration of $9.8 m / s^{2}$ parallel to the plane upward. A bob is suspended by a string from the roof. The angle in degrees which the string makes with the vertical is: (Assume that the bob does not move relative to car and $g = 9.8 m / s^{2}$ )

Discussion

1921.	how to find the direction by right hand thumb rule
Answer» how to find the direction by right hand thumb rule

Discussion

1922.	n(U)=50,n(A)=20,(n(U)-n(AUB))=18 then n( B-A)=?
Answer» n(U)=50,n(A)=20,(n(U)-n(AUB))=18 then n( B-A)=?

Discussion

1923.	31.What are the properties of a battery
Answer» 31.What are the properties of a battery

Discussion

1924.	A square frame of side l carries a current I and produces a magnetic field B at its center, The same current is passed through a circular coil having same perimeter as that of square. The field at the center of the circular coil is B1. Then the ratio B1B is-
Answer» A square frame of side $l$ carries a current $I$ and produces a magnetic field $B$ at its center, The same current is passed through a circular coil having same perimeter as that of square. The field at the center of the circular coil is $B_{1}$ . Then the ratio $\frac{B_{1}}{B}$ is-

Discussion

1925.	Does pure water conduct electricity? If not, what can we do to make it conducting? Does rain water conduct electricity?
Answer» Does pure water conduct electricity? If not, what can we do to make it conducting? Does rain water conduct electricity?

Discussion

1926.	what is the meaning of amplitude ?
Answer» what is the meaning of amplitude ?

Discussion

1927.	Significance of electric field and Gauss theorm
Answer» Significance of electric field and Gauss theorm

Discussion

1928.	Which of the following sets cannot enter into the list of fundamental quantities in any system of units? (a) length, mass and velocity (b) length, time and velocity (c mass, time and velocity (d) length, time and mass
Answer» Which of the following sets cannot enter into the list of fundamental quantities in any system of units? (a) length, mass and velocity (b) length, time and velocity (c mass, time and velocity (d) length, time and mass

Discussion

1929.	Two particals 1 &2 move with constant velocity v1 and v2 along two mutually perpendicular straight lines towards intersection point O. At a moment t=O the particals were located at the distance l1 and l2 from point o . How soon will the distance between two particals become the smallest? What it is equal to?
Answer» Two particals 1 &2 move with constant velocity v1 and v2 along two mutually perpendicular straight lines towards intersection point O. At a moment t=O the particals were located at the distance l1 and l2 from point o . How soon will the distance between two particals become the smallest? What it is equal to?

Discussion

1930.	97.For the arrangement shown in the given figure,the maximum value of m' , for which blocks will not accelerate is
Answer» 97.For the arrangement shown in the given figure,the maximum value of m' , for which blocks will not accelerate is

Discussion

1931.	A stone is dropped from a bridge and it reaches the ground in 4 seconds. The height of the bridge is
Answer» A stone is dropped from a bridge and it reaches the ground in $4$ seconds. The height of the bridge is

Discussion

1932.	What is mean by dimensional homogeneity?
Answer» What is mean by dimensional homogeneity?

Discussion

1933.	A body of mass 5 kg falls from a height of 30 metres. If all of its mechanical energy is converted into heat, then heat produced will be[Take g=9.8 m/s2 and J=4.2 J/cal]
Answer» A body of mass $5 kg$ falls from a height of $30 metres$ . If all of its mechanical energy is converted into heat, then heat produced will be $[Take g = 9.8 {m/s}^{2} and J = 4.2 J/cal]$

Discussion

1934.	The energy required to accelerate a car from 10m/s to 20m/s is x times the energy required to accelerate the same car from 0 to 10m/s.calculate the value of x?
Answer» The energy required to accelerate a car from 10m/s to 20m/s is x times the energy required to accelerate the same car from 0 to 10m/s.calculate the value of x?

Discussion

1935.	Figure 14.26 (a) shows a spring of force constant k clamped rigidly at one end anda mass m attached to its free end. A force F applied at the free end stretches thespring. Figure 14.26 (b) shows the same spring with both ends free and attached toa mass m at either end. Each end of the spring in Fig. 14.26(b) is stretched by thesame force F. (a) What is the maximum extension of the spring in the two cases ? (b) If the mass in Fig. (a) and the two masses in Fig. (b) are released, what is the period of oscillation in each case ?
Answer» Figure 14.26 (a) shows a spring of force constant k clamped rigidly at one end anda mass m attached to its free end. A force F applied at the free end stretches thespring. Figure 14.26 (b) shows the same spring with both ends free and attached toa mass m at either end. Each end of the spring in Fig. 14.26(b) is stretched by thesame force F. (a) What is the maximum extension of the spring in the two cases ? (b) If the mass in Fig. (a) and the two masses in Fig. (b) are released, what is the period of oscillation in each case ?

Discussion

1936.	Define rigidity.
Answer» Define rigidity.

Discussion

1937.	A body float with 1/3 of its volume outside water and 3/4 of its volume outside another liquid. the density of another liquid is
Answer» A body float with 1/3 of its volume outside water and 3/4 of its volume outside another liquid. the density of another liquid is

Discussion

1938.	. A ball is thrown upwards from the groundwith an initial speed of u. The ball is at aheight of 80m at two times, the time intervalbeing 6s. Magnitude of u:a. 30 m/s b. 50 m/s c. 20 m/s d. 10 m/s
Answer» . A ball is thrown upwards from the ground with an initial speed of u. The ball is at a height of 80m at two times, the time interval being 6s. Magnitude of u: a. 30 m/s b. 50 m/s c. 20 m/s d. 10 m/s

Discussion

1939.	The heat capacity of object A is is twice the object B .initially B is at 300K and A is at 450. They are placed in thermal contact and the combination is isolated.the final temperature of both object is
Answer» The heat capacity of object A is is twice the object B .initially B is at 300K and A is at 450. They are placed in thermal contact and the combination is isolated.the final temperature of both object is

Discussion

1940.	The work done in turning a magnet of magnetic moment M by an angle of 90∘ from the meridian is n times the corresponding work done to turn it through an angle of 60∘.
Answer» The work done in turning a magnet of magnetic moment M by an angle of $90^{\circ}$ from the meridian is n times the corresponding work done to turn it through an angle of $60^{\circ}$ .

Discussion

1941.	A point object of mass m moving horizontally hits the uniform solid disc and stick to it. The disc is resting on a horizontal frictionless surface and pivoted at its centre as shown in figure. Find out the MOI of the disc if it rotates with angular velocity ω=v5R after the strike.
Answer» A point object of mass $m$ moving horizontally hits the uniform solid disc and stick to it. The disc is resting on a horizontal frictionless surface and pivoted at its centre as shown in figure. Find out the $M O I$ of the disc if it rotates with angular velocity $ω = \frac{v}{5 R}$ after the strike.

Discussion

1942.	Out of four basic forces in nature which one is strongest and weakest ? Why?
Answer» Out of four basic forces in nature which one is strongest and weakest ? Why?

Discussion

1943.	A spherical ball of radius 0.05 m and density 0.5g/cc floats in water filled in a container accelerating vertically upwards with an acceleration of 4g m/s^2 .The fraction of volume of the ball immersed in the liquid will be\::
Answer» A spherical ball of radius 0.05 m and density 0.5g/cc floats in water filled in a container accelerating vertically upwards with an acceleration of 4g m/s^2 .The fraction of volume of the ball immersed in the liquid will be\::

Discussion

1944.	Find the magnitude of →B, if →B makes an angle of 37∘ West of North and →C makes an angle of 45∘ North of East and →A has magnitude equal to 7√5 and →C has magnitude equal to 10√2. (Given →A+→B+→C=0)
Answer» Find the magnitude of $\to B$ , if $\to B$ makes an angle of $37^{\circ}$ West of North and $\to C$ makes an angle of $45^{\circ}$ North of East and $\to A$ has magnitude equal to $7 \sqrt{5}$ and $\to C$ has magnitude equal to $10 \sqrt{2}$ . (Given $\to A + \to B + \to C = 0$ )

Discussion

1945.	A jet airplane travelling at the speed of 400 km h ejects its products of combustion at the speed of1200 km h relative to the jet plane. What is the speed of the latter with respect to an observer on theground?
Answer» A jet airplane travelling at the speed of 400 km h ejects its products of combustion at the speed of 1200 km h relative to the jet plane. What is the speed of the latter with respect to an observer on the ground?

Discussion

1946.	A water particle of mass 10.0 mg and having a charge of 1.50×10−6C stays suspended in a room. What is the magnitude of electric field in the room? what is its direction?
Answer» A water particle of mass 10.0 mg and having a charge of $1.50 \times 10^{- 6} C$ stays suspended in a room. What is the magnitude of electric field in the room? what is its direction?

1946.

A water particle of mass 10.0 mg and having a charge of 1.50×10−6C stays suspended in a room. What is the magnitude of electric field in the room? what is its direction?

Answer»

A water particle of mass 10.0 mg and having a charge of $1.50 \times 10^{- 6} C$ stays suspended in a room. What is the magnitude of electric field in the room? what is its direction?

Discussion

1947.	4 m long rope, having a mass of 40 g is fixed at one end and is tied to a light string at the other end. Find the tension in the string if the difference between frequencies of consecutive overtones is 40 Hz.
Answer» $4 m$ long rope, having a mass of $40 g$ is fixed at one end and is tied to a light string at the other end. Find the tension in the string if the difference between frequencies of consecutive overtones is $40 Hz$ .

Discussion

1948.	A single slit of width a is illuminated by violet light of wavelength 4000 ˙A and the width of the central maximum is measured as y. When half of the slit width is covered and illuminated by yellow light of wavelength 6000 ˙A, the width of the central maxima is
Answer» A single slit of width $a$ is illuminated by violet light of wavelength $4000 ˙ A$ and the width of the central maximum is measured as $y$ . When half of the slit width is covered and illuminated by yellow light of wavelength $6000 ˙ A$ , the width of the central maxima is

Discussion

1949.	In an experiment on determining the velocity of a pulse propagating through a stretched string, the stopwatch should be started and stopped at instants corresponding to the ones shown in :(1) Fig. 1 and Fig. 2(2) Fig. 1 and Fig. 3(3) Fig. 2 and Fig. 1(4) Fig. 2 and Fig. 3
Answer» In an experiment on determining the velocity of a pulse propagating through a stretched string, the stopwatch should be started and stopped at instants corresponding to the ones shown in : (1) Fig. 1 and Fig. 2 (2) Fig. 1 and Fig. 3 (3) Fig. 2 and Fig. 1 (4) Fig. 2 and Fig. 3

Discussion

1950.	14. A spherical metal plate of radius 1.5cm is charged with 10micro coulomb situated in air.find mechanical force acting on side of plate.If the same spherical plate carrying same charge were kept in acetone what would be the magnitude of mechanical force.(k acetone=27)
Answer» 14. A spherical metal plate of radius 1.5cm is charged with 10micro coulomb situated in air.find mechanical force acting on side of plate.If the same spherical plate carrying same charge were kept in acetone what would be the magnitude of mechanical force.(k acetone=27)

Discussion

Explore topic-wise InterviewSolutions in .

An express train is moving with a velocity v1. Its driver finds another train is moving on the same track in the same direction with velocity v2(v2&lt;v1). To escape collision, driver applies a retardation a on the train. The minimum time to escape the collision is

A force →F=6x^i+2y^j displaces a body from →r1=3^i+8^j to →r2=5^i−4^j. Find the work done by the force.

The electric field in a certain region is given by, →E=(5^i) kV/m. The potential difference (VB−VA) between two points A and B having co-ordinates (4,0,0) and (10,3,0) respectively, is equal to -(co-ordinates x,y and z are in metre)

Find d²y/dx²:x=at²y=2at

A graph is plotted between magnitude of electric field (upon the y axis)and the distance upon the perpendicular bisector of long line charge(upon x axis).Draw the graph

A soap film has been developed over a wire loop. If surface tension of the soap solution is 0.015 N/m, find the tension in the thread loop of length 12.56 cm which is kept over the soap film, when the soap film inside it is pricked.

The average kinetic energy of one mole of gas per degree of freedom (on the basis of theory of gases)

An electron already accelerated through 100 V is further accelerated through an additional potential difference of 25 V.The fractional change in its de Broglie wavelength will be(approx)0.1050.2120.3330.452

The kinetic energy of a projectile at its highest position is K. If the range of the projectile is 4 times the height of the projectile then find the initial kinetic energy of the projectile .

A weight W is supported by two strings inclined at 60∘ and 30∘ to vertical. The tensions in the strings are T1 and T2 as shown. If these tensions have to be determined in terms of W using a triangle of forces, then which of the following triangles should be drawn ?(The blocks in equilibrium)

Curves of two waves propagating in the same medium is shown. Here, y is displacement in m and t is time in s. Find the ratio of their average intensities?

A cell of constant emf first connected to a resistance R1 and then connected to a resistance R2. If power delivered in both cases is same, then the internal resistance of the cell is

Consider a hollow conducting cylinder with inner and outer radii 10 cm and 50 cm respectively and it carries a current I=9 A. Find the magnitude of magnetic induction at 30 cm from the axis of the cylinder.

If converging line falls on concave lens then lines become parallel and if parallel lines fall on it then lines divergeIs this statement true??

Two travelling waves y = 0.10sin(3t +4πx) metres and y= 0.2sin(3t - 5πx) metres meet at t =0 what is the displacement at x=4.5 at this moment

Four metal plates numbered 1,2,3 and 4 are arranged as shown below. The area of each plate is A=10 cm2 and separation between adjacent plates is d=1.5 mm. The capacitance of the arrangement is

A point charge q is placed inside a conducting spherical shell of inner radius 2R and outer radius 3R at a distance of R from the centre of the shell. The electric potential at the centre of shell will be 14πϵ0 times.

Two air bubbles are joined to form a double bubble.If 3 cm and 4 cm are the individual radii of the two bubbles then the radius and the sense ofcurvature of the internal film surface common to both the bubbles is

how to find the direction by right hand thumb rule

n(U)=50,n(A)=20,(n(U)-n(AUB))=18 then n( B-A)=?

31.What are the properties of a battery

A square frame of side l carries a current I and produces a magnetic field B at its center, The same current is passed through a circular coil having same perimeter as that of square. The field at the center of the circular coil is B1. Then the ratio B1B is-

Does pure water conduct electricity? If not, what can we do to make it conducting? Does rain water conduct electricity?

what is the meaning of amplitude ?

Significance of electric field and Gauss theorm

Which of the following sets cannot enter into the list of fundamental quantities in any system of units? (a) length, mass and velocity (b) length, time and velocity (c mass, time and velocity (d) length, time and mass

97.For the arrangement shown in the given figure,the maximum value of m' , for which blocks will not accelerate is

A stone is dropped from a bridge and it reaches the ground in 4 seconds. The height of the bridge is

What is mean by dimensional homogeneity?

A body of mass 5 kg falls from a height of 30 metres. If all of its mechanical energy is converted into heat, then heat produced will be[Take g=9.8 m/s2 and J=4.2 J/cal]

The energy required to accelerate a car from 10m/s to 20m/s is x times the energy required to accelerate the same car from 0 to 10m/s.calculate the value of x?

Define rigidity.

A body float with 1/3 of its volume outside water and 3/4 of its volume outside another liquid. the density of another liquid is

. A ball is thrown upwards from the groundwith an initial speed of u. The ball is at aheight of 80m at two times, the time intervalbeing 6s. Magnitude of u:a. 30 m/s b. 50 m/s c. 20 m/s d. 10 m/s

The heat capacity of object A is is twice the object B .initially B is at 300K and A is at 450. They are placed in thermal contact and the combination is isolated.the final temperature of both object is

The work done in turning a magnet of magnetic moment M by an angle of 90∘ from the meridian is n times the corresponding work done to turn it through an angle of 60∘.

A point object of mass m moving horizontally hits the uniform solid disc and stick to it. The disc is resting on a horizontal frictionless surface and pivoted at its centre as shown in figure. Find out the MOI of the disc if it rotates with angular velocity ω=v5R after the strike.

Out of four basic forces in nature which one is strongest and weakest ? Why?

A spherical ball of radius 0.05 m and density 0.5g/cc floats in water filled in a container accelerating vertically upwards with an acceleration of 4g m/s^2 .The fraction of volume of the ball immersed in the liquid will be\::

Find the magnitude of →B, if →B makes an angle of 37∘ West of North and →C makes an angle of 45∘ North of East and →A has magnitude equal to 7√5 and →C has magnitude equal to 10√2. (Given →A+→B+→C=0)

A jet airplane travelling at the speed of 400 km h ejects its products of combustion at the speed of1200 km h relative to the jet plane. What is the speed of the latter with respect to an observer on theground?

A water particle of mass 10.0 mg and having a charge of 1.50×10−6C stays suspended in a room. What is the magnitude of electric field in the room? what is its direction?

4 m long rope, having a mass of 40 g is fixed at one end and is tied to a light string at the other end. Find the tension in the string if the difference between frequencies of consecutive overtones is 40 Hz.

A single slit of width a is illuminated by violet light of wavelength 4000 ˙A and the width of the central maximum is measured as y. When half of the slit width is covered and illuminated by yellow light of wavelength 6000 ˙A, the width of the central maxima is

In an experiment on determining the velocity of a pulse propagating through a stretched string, the stopwatch should be started and stopped at instants corresponding to the ones shown in :(1) Fig. 1 and Fig. 2(2) Fig. 1 and Fig. 3(3) Fig. 2 and Fig. 1(4) Fig. 2 and Fig. 3

14. A spherical metal plate of radius 1.5cm is charged with 10micro coulomb situated in air.find mechanical force acting on side of plate.If the same spherical plate carrying same charge were kept in acetone what would be the magnitude of mechanical force.(k acetone=27)

An express train is moving with a velocity v1. Its driver finds another train is moving on the same track in the same direction with velocity v2(v2<v1). To escape collision, driver applies a retardation a on the train. The minimum time to escape the collision is