50278 + Interview Questions in Physics

1.	Figure 5.16 shows the position-time graph of a particle of mass 4 kg. What is the (a) force on the particle for t<0,t>4s,0<t<4 s? (b) impulse at t = 0 and t = 4 s? (Consider one-dimensional motion only).
Answer» Figure 5.16 shows the position-time graph of a particle of mass 4 kg. What is the (a) force on the particle for $t < 0, t > 4 s, 0 < t < 4 s$ ? (b) impulse at t = 0 and t = 4 s? (Consider one-dimensional motion only).

Discussion

2.	Resistance of a wire is 20 ohm, it is stretched upto three times of length, then its new resistance will be
Answer» Resistance of a wire is 20 ohm, it is stretched upto three times of length, then its new resistance will be

Discussion

3.	A parallel plate capacitor of capacitance C is charged to a potential V. It is then connected to another uncharged capacitor having the same capacitance. Find out the ratio of the energy stored in the combined system to that stored initially in the single capacitor.
Answer» A parallel plate capacitor of capacitance C is charged to a potential V. It is then connected to another uncharged capacitor having the same capacitance. Find out the ratio of the energy stored in the combined system to that stored initially in the single capacitor.

Discussion

4.	Who discovered and first used the constant h = 6.6 x 10-34 J.s?
Answer» Who discovered and first used the constant h = 6.6 x 10^-34 J.s?

Discussion

5.	What is electric dipole moment?
Answer» What is electric dipole moment?

Discussion

6.	Given three resistors of 2Ω,4Ω and 6Ω, what will be the minimum equivalent resistance one can obtain through their various arrangements?
Answer» Given three resistors of $2 Ω, 4 Ω a n d 6 Ω$ , what will be the minimum equivalent resistance one can obtain through their various arrangements?

Discussion

7.	Consider the situation shown in figure. The force F is equal to the m2g/2.If the area of cross section of the string is A and its Young modulus Y, find the strain developed in it. The string is light and there is no friction anywhere.
Answer» Consider the situation shown in figure. The force F is equal to the $m_{2} g / 2$ .If the area of cross section of the string is A and its Young modulus Y, find the strain developed in it. The string is light and there is no friction anywhere.

Discussion

8.	A small block of mass m slides along a smooth frictionless track as shown in the figure. (i) If it starts from rest at P, what is the resultant force acting on it at Q? (ii) At what height above the bottom of the loop should the block be released so that the force it exerts against the track at the top of the loop equals its weight?
Answer» A small block of mass $m$ slides along a smooth frictionless track as shown in the figure. (i) If it starts from rest at $P$ , what is the resultant force acting on it at $Q$ ? (ii) At what height above the bottom of the loop should the block be released so that the force it exerts against the track at the top of the loop equals its weight?

Discussion

9.	When a person leaves his home for sigthseeing by his car, the meter reads 12352 km, When he returns home after two hours the reading is 12413 km. (a) What is the average speed of the car during this period? (b)What is the average velocity.
Answer» When a person leaves his home for sigthseeing by his car, the meter reads 12352 km, When he returns home after two hours the reading is 12413 km. (a) What is the average speed of the car during this period? (b)What is the average velocity.

9.

When a person leaves his home for sigthseeing by his car, the meter reads 12352 km, When he returns home after two hours the reading is 12413 km. (a) What is the average speed of the car during this period? (b)What is the average velocity.

Answer»

When a person leaves his home for sigthseeing by his car, the meter reads 12352 km, When he returns home after two hours the reading is 12413 km.

(a) What is the average speed of the car during this period?

(b)What is the average velocity.

Discussion

10.	A conducting wire ab of length l, resistance r and mass m starts sliding at t = 0 down a smooth, vertical, thick pair of connected rails as shown in figure (38-E24). A uniform magnetic field B exists in the space in a direction perpendicular to the plane of the rails (a) Write the induced emf in the loop at an instant ; when the speed of the wire is v. (b) What would be the magnitude and direction of the induced current in the wire ? (c) Find the downward acceleration of the wire at this instant. (d) After sufficient time, the wire starts moving with a constant velocity. Find this velocity nit (e) Find the velocity of the wire as a function of time ft) Find the displacement of the wire as a function ai time. (g) Show that the rate of heat developed in the wire is equal to the rate at which the gravitational potential energy is decreased after steady state is reached.
Answer» A conducting wire ab of length l, resistance r and mass m starts sliding at t = 0 down a smooth, vertical, thick pair of connected rails as shown in figure (38-E24). A uniform magnetic field B exists in the space in a direction perpendicular to the plane of the rails (a) Write the induced emf in the loop at an instant ; when the speed of the wire is v. (b) What would be the magnitude and direction of the induced current in the wire ? (c) Find the downward acceleration of the wire at this instant. (d) After sufficient time, the wire starts moving with a constant velocity. Find this velocity nit (e) Find the velocity of the wire as a function of time ft) Find the displacement of the wire as a function ai time. (g) Show that the rate of heat developed in the wire is equal to the rate at which the gravitational potential energy is decreased after steady state is reached.

10.

A conducting wire ab of length l, resistance r and mass m starts sliding at t = 0 down a smooth, vertical, thick pair of connected rails as shown in figure (38-E24). A uniform magnetic field B exists in the space in a direction perpendicular to the plane of the rails (a) Write the induced emf in the loop at an instant ; when the speed of the wire is v. (b) What would be the magnitude and direction of the induced current in the wire ? (c) Find the downward acceleration of the wire at this instant. (d) After sufficient time, the wire starts moving with a constant velocity. Find this velocity nit (e) Find the velocity of the wire as a function of time ft) Find the displacement of the wire as a function ai time. (g) Show that the rate of heat developed in the wire is equal to the rate at which the gravitational potential energy is decreased after steady state is reached.

Answer»

A conducting wire ab of length l, resistance r and mass m starts sliding at t = 0 down a smooth, vertical, thick pair of connected rails as shown in figure (38-E24). A

uniform magnetic field B exists in the space in a direction perpendicular to the plane of the rails (a) Write the induced emf in the loop at an instant ; when the speed of the wire is v. (b) What would be the magnitude and direction of the induced current in the wire ? (c) Find the downward acceleration of the wire at this instant. (d) After sufficient time, the wire starts moving with a constant velocity. Find this velocity nit (e) Find the velocity of the wire as a function of time ft) Find the displacement of the wire as a function ai time. (g) Show that the rate of heat developed in the wire is equal to the rate at which the gravitational potential energy is decreased after steady state is reached.

Discussion

11.	A particle is projected at an angle of 60∘ above the horizontal with a speed of 10 m/s. After some time, the direction of its velocity makes an angle of 30∘ above the horizontal. The speed of the particle at this instant is
Answer» A particle is projected at an angle of $60^{\circ}$ above the horizontal with a speed of $10 m / s$ . After some time, the direction of its velocity makes an angle of $30^{\circ}$ above the horizontal. The speed of the particle at this instant is

Discussion

12.	Time velocity graphs for 2 objects A and B are straight lines inclined 600 and 300 with the time axis. Then the accelerations of A and B are in the ratio?
Answer» Time velocity graphs for 2 objects A and B are straight lines inclined 60⁰ and 30⁰ with the time axis. Then the accelerations of A and B are in the ratio?

Discussion

13.	The voltage of an ac supply varies with time (t) as V=120 sin 100 π t cos 100 π t. The maximum voltage and frequency respectively are
Answer» The voltage of an ac supply varies with time (t) as $V = 120 s i n 100 π t c o s 100 π t$ . The maximum voltage and frequency respectively are

Discussion

14.	The electric force experienced by a charge of 1.0×10−6C is 1.5×10−3N. N. Fin the magnitude of the electric field at the position of the charge.
Answer» The electric force experienced by a charge of $1.0 \times 10^{- 6} C$ is $1.5 \times 10^{- 3} N .$ N. Fin the magnitude of the electric field at the position of the charge.

Discussion

15.	4 moles of an ideal gas is at 0∘C. At constant pressure it is heated to double its volume, then its final temperature will be
Answer» 4 moles of an ideal gas is at $0^{\circ} C$ . At constant pressure it is heated to double its volume, then its final temperature will be

Discussion

16.	A bomber plane moves horizontally with a speed of 500 m/s and a bomb released from it, strikes the ground in 10 sec. Angle at which it strikes the ground will be (g = 10 m/s2)
Answer» A bomber plane moves horizontally with a speed of 500 m/s and a bomb released from it, strikes the ground in 10 sec. Angle at which it strikes the ground will be $(g = 10 m / s^{2})$

Discussion

17.	With a certain cell, the balance point is obtained at 0.60 m from one end of the potentiometer. With another cell whose emf differs from that of the first by 0.1 V, the balance point is obtained at 0.55 m. Then, the two emf’s are
Answer» With a certain cell, the balance point is obtained at 0.60 m from one end of the potentiometer. With another cell whose emf differs from that of the first by 0.1 V, the balance point is obtained at 0.55 m. Then, the two emf’s are

Discussion

18.	A car is moving on a circular road of radius of curvature 500 m. If the coefficient of friction is 0.8 and g=10 m/s2, the maximum speed of the car can have without slipping is in (km/hr).
Answer» A car is moving on a circular road of radius of curvature $500 m$ . If the coefficient of friction is $0.8$ and $g = 10 {m/s}^{2}$ , the maximum speed of the car can have without slipping is in $(km/hr)$ .

Discussion

19.	Name the essential components of a communication system.
Answer» Name the essential components of a communication system.

Discussion

20.	It is known that atoms have electrons, protons ,neutrons if the mass of neutron is assumed to be half of its original value whereas that of proton is assumed to be twice the original value ,then the atomic mass of 6C14 will be. A)14.3%less than the original B)14.3%greater than the orginal C)28.6%less than the original D)28.6%greater than the original.
Answer» It is known that atoms have electrons, protons ,neutrons if the mass of neutron is assumed to be half of its original value whereas that of proton is assumed to be twice the original value ,then the atomic mass of 6C¹⁴ will be. A)14.3%less than the original B)14.3%greater than the orginal C)28.6%less than the original D)28.6%greater than the original.

Discussion

21.	A coil having an inductance L and a resistance R is connected to a battery of emf ε Find the time taken for the magnetic energy stored in the circuit to change from one fourth of th steady - state to half of the steady state value.
Answer» A coil having an inductance L and a resistance R is connected to a battery of emf $ε$ Find the time taken for the magnetic energy stored in the circuit to change from one fourth of th steady - state to half of the steady state value.

Discussion

22.	An inverted bell lying at the bottom of a lake 47.6 m deep has 50 cm3 of air trapped in it. The bell is brought to the surface of the lake. The volume of the trapped air will be (atmospheric pressure = 70 cm of Hg and density of Hg = 13. 6 g / cm3)
Answer» An inverted bell lying at the bottom of a lake 47.6 m deep has 50 cm3 of air trapped in it. The bell is brought to the surface of the lake. The volume of the trapped air will be (atmospheric pressure = 70 cm of Hg and density of Hg = 13. 6 g / $c m^{3}$ )

Discussion

23.	A body falls freely from rest. It covers as much distance in the last second of its motion as covered in the first three seconds. The body has fallen for a time of ( in seconds upto two decimals)
Answer» A body falls freely from rest. It covers as much distance in the last second of its motion as covered in the first three seconds. The body has fallen for a time of ( in seconds upto two decimals)

Discussion

24.	Why don't clouds fall to the earth due to gravity?
Answer» Why don't clouds fall to the earth due to gravity?

Discussion

25.	What is the difference between shells, subshells and orbitals??
Answer» What is the difference between shells, subshells and orbitals??

Discussion

26.	If the magnetic flux linked with a coil through which a current of x A is set up is y Wb, then the coefficient of self-inductance of the coil is:
Answer» If the magnetic flux linked with a coil through which a current of x A is set up is y Wb, then the coefficient of self-inductance of the coil is:

Discussion

27.	The arithmetic mean of set of observations is ¯x If each observation is divided by α and then is increased by 10, then the mean of new series is
Answer» The arithmetic mean of set of observations is $¯ x$ If each observation is divided by $α$ and then is increased by $10$ , then the mean of new series is

Discussion

28.	An object is displaced from point A(2,0,0) m to a point B(1,0,4) m under the influence of a force →F=4x^i−2z^k. The workdone by this force is
Answer» An object is displaced from point $A (2, 0, 0) m$ to a point $B (1, 0, 4) m$ under the influence of a force $\to F = 4 x^i - 2 z^k .$ The workdone by this force is

Discussion

29.	Why Rutherford chooses gold foil
Answer» Why Rutherford chooses gold foil

Discussion

30.	Calculate the number of gold atoms in 300 mg of a gold ring of 20-carat gold.
Answer» Calculate the number of gold atoms in 300 mg of a gold ring of 20-carat gold.

Discussion

31.	A lead ball strikes a wall and falls down, a tennis ball having the same mass and velocity strikes the wall and bounces back. Check the correct statement
Answer» A lead ball strikes a wall and falls down, a tennis ball having the same mass and velocity strikes the wall and bounces back. Check the correct statement

Discussion

32.	According to heisenberg uncertainty principle
Answer» According to heisenberg uncertainty principle

32.

According to heisenberg uncertainty principle

Answer»

According to heisenberg uncertainty principle

Discussion

33.	An operator sitting in his base camp sends a sound signal of frequency 400 Hz. The signal is reflected back from a car moving towards him. The frequency of the reflected sound is found to be 410 Hz. Find the speed of the car. Speed of sound in air = 324ms−1.
Answer» An operator sitting in his base camp sends a sound signal of frequency 400 Hz. The signal is reflected back from a car moving towards him. The frequency of the reflected sound is found to be 410 Hz. Find the speed of the car. Speed of sound in air = $324 m s^{- 1}$ .

Discussion

34.	Four charge particles α, proton, deuteron and Li+++ are projected in a uniform magnetic field perpendicular to velocity. Consider the radius of the particle having least radius out of these to be r, List-1 gives the particles and List-2 gives value of n, where nr is the radius of the particle. Match the entries correctly in the lists if momentum of each particle is same. List-1List-2(I)α(P)1(II)Proton(Q)2(III)Deuteron(R)3(IV)Li+++(S)3√7(T)3√2√7(U)32
Answer» Four charge particles $α$ , proton, deuteron and $L i^{+ + +}$ are projected in a uniform magnetic field perpendicular to velocity. Consider the radius of the particle having least radius out of these to be r, List-1 gives the particles and List-2 gives value of n, where nr is the radius of the particle. Match the entries correctly in the lists if momentum of each particle is same. $\begin{matrix} List-1 & List-2 (I) & α & (P) & 1 (II) & Proton & (Q) & 2 (III) & Deuteron & (R) & 3 (IV) & L i^{+ + +} & (S) & \frac{3}{\sqrt{7}} (T) & \frac{3 \sqrt{2}}{\sqrt{7}} (U) & \frac{3}{2} \end{matrix}$

Discussion

35.	The sensitivity of a moving coil galvanometer can be increased by
Answer» The sensitivity of a moving coil galvanometer can be increased by

Discussion

36.	A wave disturbance in a medium is described by y(x,t)=0.02 cos ⎧⎪⎩50πt+π2⎫⎪⎭cos(10πx), where x and y are in metres and t in seconds
Answer» A wave disturbance in a medium is described by $y (x, t) = 0.02 c o s ⎧ ⎪ ⎩ 50 π t + \frac{π}{2} ⎫ ⎪ ⎭ c o s (10 π x)$ , where x and y are in metres and t in seconds

Discussion

37.	A 3 cm tall object is placed at a distance of 7.5 cm from a convex mirror of focal length 6 cm. Find the location, size and the nature of the image.
Answer» A 3 cm tall object is placed at a distance of 7.5 cm from a convex mirror of focal length 6 cm. Find the location, size and the nature of the image.

Discussion

38.	A particle is kept at rest at the top of a sphere of diameter 42 m. When disturbed slightly, it slides down. At what height h from the bottom, the particle will leave the sphere
Answer» A particle is kept at rest at the top of a sphere of diameter $42 m$ . When disturbed slightly, it slides down. At what height $h$ from the bottom, the particle will leave the sphere

Discussion

39.	The displacement of a particle varies with time t as: s=αt2−βt3. Determine the time (t) at which acceleration of the particle becomes 0.
Answer» The displacement of a particle varies with time $t$ as: $s = α t^{2} - β t^{3}$ . Determine the time $(t)$ at which acceleration of the particle becomes $0$ .

Discussion

40.	A man is standing at a spring platform. Reading of spring balance is 60 kg wt. If man jumps outside platform, then reading of spring balance
Answer» A man is standing at a spring platform. Reading of spring balance is 60 kg wt. If man jumps outside platform, then reading of spring balance

Discussion

41.	A light ray is incident on an equilateral prism of refractive index 5/3. What should be the angle of incidence such that the ray grazes on the second surface ?
Answer» A light ray is incident on an equilateral prism of refractive index 5/3. What should be the angle of incidence such that the ray grazes on the second surface ?

Discussion

42.	Particle A is released from a point P on a smooth inclined plane inclined at an angle α with the horizontal. At the same instant another particle B is projected with initial velocity u making an angle β with the horizontal. Both the particles meet again on the inclined plane. Find the relation between α and β
Answer» Particle A is released from a point P on a smooth inclined plane inclined at an angle $α$ with the horizontal. At the same instant another particle B is projected with initial velocity $u$ making an angle $β$ with the horizontal. Both the particles meet again on the inclined plane. Find the relation between $α$ and $β$

Discussion

43.	A hydraulic automobile lift is designed to lift cars with a maximum mass of 300 kg. The area of cross-section of the piston carrying the load is 500 cm2. What maximum pressure would smaller piston have to bear?
Answer» A hydraulic automobile lift is designed to lift cars with a maximum mass of $300 kg$ . The area of cross-section of the piston carrying the load is $500 {cm}^{2}$ . What maximum pressure would smaller piston have to bear?

Discussion

44.	A man on the top of a vertical tower observes a car moving at a uniform speed towards the tower on a horizonatal road. If it takes 18 min. for the angle of depression of the car to change from 30° to 45° ; then after this, the time taken (in min.) by the car to reach the foot of the tower, is:
Answer» A man on the top of a vertical tower observes a car moving at a uniform speed towards the tower on a horizonatal road. If it takes $18$ min. for the angle of depression of the car to change from $30 ° t o 45 °$ ; then after this, the time taken (in min.) by the car to reach the foot of the tower, is:

Discussion

45.	What is an inertial frame of reference?
Answer» What is an inertial frame of reference?

Discussion

46.	Let ΔE denote the energy gap between the valence band and the conduction band. The population of conduction electrons (and of the holes) is roughly proportional to e−ΔE/2kT. Find the ratio of the concentration of conduction electrons in diamond to that in silicon at room temperature 300 K. ΔE for silicon is 1.1 eV and for diamond is 6.0 eV. How many conduction electrons are likely to be in one cubic metre of diamond ?
Answer» Let $Δ E$ denote the energy gap between the valence band and the conduction band. The population of conduction electrons (and of the holes) is roughly proportional to $e^{- Δ E / 2 k T} .$ Find the ratio of the concentration of conduction electrons in diamond to that in silicon at room temperature 300 K. $Δ E$ for silicon is 1.1 eV and for diamond is 6.0 eV. How many conduction electrons are likely to be in one cubic metre of diamond ?

Discussion

47.	A tightly-wound, long solenoid has n turns per unit length, a radius r and carries a current i. A particle having charge q and mass m is projected from a point on the axis in a direction perpendicular to the axis. What can be the maximum speed for which the particle does not strike the solenoid ?
Answer» A tightly-wound, long solenoid has n turns per unit length, a radius r and carries a current i. A particle having charge q and mass m is projected from a point on the axis in a direction perpendicular to the axis. What can be the maximum speed for which the particle does not strike the solenoid ?

Discussion

48.	A simple pendulum hanging from the ceiling of a stationary lift has a time period T1. When the lift moves downward with constant velocity, the time period is T2, then
Answer» A simple pendulum hanging from the ceiling of a stationary lift has a time period $T_{1}$ . When the lift moves downward with constant velocity, the time period is $T_{2}$ , then

Discussion

49.	The infinite sheets of uniform charge density 10μCm2,−10μCm2and5μCm2 are placed in vacuum as shown. The direction of field intensity at points A and B are respectively?
Answer» The infinite sheets of uniform charge density $10 \frac{μ C}{m^{2}}, - 10 \frac{μ C}{m^{2}} a n d 5 \frac{μ C}{m^{2}}$ are placed in vacuum as shown. The direction of field intensity at points A and B are respectively?

49.

The infinite sheets of uniform charge density 10μCm2,−10μCm2and5μCm2 are placed in vacuum as shown. The direction of field intensity at points A and B are respectively?

Answer»

The infinite sheets of uniform charge density $10 \frac{μ C}{m^{2}}, - 10 \frac{μ C}{m^{2}} a n d 5 \frac{μ C}{m^{2}}$ are placed in vacuum as shown. The direction of field intensity at points A and B are respectively?

Discussion

50.	A seconds pendulum clock made up of a wire shows correct time at 25 ∘C. How much time does the clock lose or gain, in one week, when the temperature is increased to 35 ∘C? [ α=1.2×10−5/ ∘C ]
Answer» A seconds pendulum clock made up of a wire shows correct time at $25^{\circ} C$ . How much time does the clock lose or gain, in one week, when the temperature is increased to $35^{\circ} C$ ? $[α = 1.2 \times 10^{- 5} /^{\circ} C]$

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Figure 5.16 shows the position-time graph of a particle of mass 4 kg. What is the (a) force on the particle for t&lt;0,t&gt;4s,0&lt;t&lt;4 s? (b) impulse at t = 0 and t = 4 s? (Consider one-dimensional motion only).

Resistance of a wire is 20 ohm, it is stretched upto three times of length, then its new resistance will be

A parallel plate capacitor of capacitance C is charged to a potential V. It is then connected to another uncharged capacitor having the same capacitance. Find out the ratio of the energy stored in the combined system to that stored initially in the single capacitor.

Who discovered and first used the constant h = 6.6 x 10-34 J.s?

What is electric dipole moment?

Given three resistors of 2Ω,4Ω and 6Ω, what will be the minimum equivalent resistance one can obtain through their various arrangements?

Consider the situation shown in figure. The force F is equal to the m2g/2.If the area of cross section of the string is A and its Young modulus Y, find the strain developed in it. The string is light and there is no friction anywhere.

When a person leaves his home for sigthseeing by his car, the meter reads 12352 km, When he returns home after two hours the reading is 12413 km. (a) What is the average speed of the car during this period? (b)What is the average velocity.

A particle is projected at an angle of 60∘ above the horizontal with a speed of 10 m/s. After some time, the direction of its velocity makes an angle of 30∘ above the horizontal. The speed of the particle at this instant is

Time velocity graphs for 2 objects A and B are straight lines inclined 600 and 300 with the time axis. Then the accelerations of A and B are in the ratio?

The voltage of an ac supply varies with time (t) as V=120 sin 100 π t cos 100 π t. The maximum voltage and frequency respectively are

The electric force experienced by a charge of 1.0×10−6C is 1.5×10−3N. N. Fin the magnitude of the electric field at the position of the charge.

4 moles of an ideal gas is at 0∘C. At constant pressure it is heated to double its volume, then its final temperature will be

A bomber plane moves horizontally with a speed of 500 m/s and a bomb released from it, strikes the ground in 10 sec. Angle at which it strikes the ground will be (g = 10 m/s2)

With a certain cell, the balance point is obtained at 0.60 m from one end of the potentiometer. With another cell whose emf differs from that of the first by 0.1 V, the balance point is obtained at 0.55 m. Then, the two emf’s are

A car is moving on a circular road of radius of curvature 500 m. If the coefficient of friction is 0.8 and g=10 m/s2, the maximum speed of the car can have without slipping is in (km/hr).

Name the essential components of a communication system.

A coil having an inductance L and a resistance R is connected to a battery of emf ε Find the time taken for the magnetic energy stored in the circuit to change from one fourth of th steady - state to half of the steady state value.

An inverted bell lying at the bottom of a lake 47.6 m deep has 50 cm3 of air trapped in it. The bell is brought to the surface of the lake. The volume of the trapped air will be (atmospheric pressure = 70 cm of Hg and density of Hg = 13. 6 g / cm3)

A body falls freely from rest. It covers as much distance in the last second of its motion as covered in the first three seconds. The body has fallen for a time of ( in seconds upto two decimals)

Why don't clouds fall to the earth due to gravity?

What is the difference between shells, subshells and orbitals??

If the magnetic flux linked with a coil through which a current of x A is set up is y Wb, then the coefficient of self-inductance of the coil is:

The arithmetic mean of set of observations is ¯x If each observation is divided by α and then is increased by 10, then the mean of new series is

An object is displaced from point A(2,0,0) m to a point B(1,0,4) m under the influence of a force →F=4x^i−2z^k. The workdone by this force is

Why Rutherford chooses gold foil

Calculate the number of gold atoms in 300 mg of a gold ring of 20-carat gold.

A lead ball strikes a wall and falls down, a tennis ball having the same mass and velocity strikes the wall and bounces back. Check the correct statement

According to heisenberg uncertainty principle

An operator sitting in his base camp sends a sound signal of frequency 400 Hz. The signal is reflected back from a car moving towards him. The frequency of the reflected sound is found to be 410 Hz. Find the speed of the car. Speed of sound in air = 324ms−1.

The sensitivity of a moving coil galvanometer can be increased by

A wave disturbance in a medium is described by y(x,t)=0.02 cos ⎧⎪⎩50πt+π2⎫⎪⎭cos(10πx), where x and y are in metres and t in seconds

A 3 cm tall object is placed at a distance of 7.5 cm from a convex mirror of focal length 6 cm. Find the location, size and the nature of the image.

A particle is kept at rest at the top of a sphere of diameter 42 m. When disturbed slightly, it slides down. At what height h from the bottom, the particle will leave the sphere

The displacement of a particle varies with time t as: s=αt2−βt3. Determine the time (t) at which acceleration of the particle becomes 0.

A man is standing at a spring platform. Reading of spring balance is 60 kg wt. If man jumps outside platform, then reading of spring balance

A light ray is incident on an equilateral prism of refractive index 5/3. What should be the angle of incidence such that the ray grazes on the second surface ?

A hydraulic automobile lift is designed to lift cars with a maximum mass of 300 kg. The area of cross-section of the piston carrying the load is 500 cm2. What maximum pressure would smaller piston have to bear?

A man on the top of a vertical tower observes a car moving at a uniform speed towards the tower on a horizonatal road. If it takes 18 min. for the angle of depression of the car to change from 30° to 45° ; then after this, the time taken (in min.) by the car to reach the foot of the tower, is:

What is an inertial frame of reference?

A tightly-wound, long solenoid has n turns per unit length, a radius r and carries a current i. A particle having charge q and mass m is projected from a point on the axis in a direction perpendicular to the axis. What can be the maximum speed for which the particle does not strike the solenoid ?

A simple pendulum hanging from the ceiling of a stationary lift has a time period T1. When the lift moves downward with constant velocity, the time period is T2, then

The infinite sheets of uniform charge density 10μCm2,−10μCm2and5μCm2 are placed in vacuum as shown. The direction of field intensity at points A and B are respectively?

A seconds pendulum clock made up of a wire shows correct time at 25 ∘C. How much time does the clock lose or gain, in one week, when the temperature is increased to 35 ∘C? [ α=1.2×10−5/ ∘C ]

Figure 5.16 shows the position-time graph of a particle of mass 4 kg. What is the (a) force on the particle for t<0,t>4s,0<t<4 s? (b) impulse at t = 0 and t = 4 s? (Consider one-dimensional motion only).