[" 19.A partlete th drepped trom rest a torge hefsh) Assume "9" to teecentient throughout the mollon.The fline folken by life foll "],[" through sueces the diffenees of "1" m cach will be "]

A particle is dropped from rest from a large height Assume g to be constant throughout the motion. The time taken by it to fall through successive distance of 1 m each will be :

A particle is dropped from rest from a large height Assume g to be constant throughout the motion. The time taken by it to fall through successive distance of 1 m each will be :

A particle is dropped from rest from a large height Assume g to be constant throughout the motion. The time taken by it to fall through successive distance of 1 m each will be :

A car P is moving with a uniform speed 5sqrt3 m//s towards a carriage of mass 9 kg at rest kept on the rails at a point B as shown in figure. The height AC is 120 m. Cannon balls of 1 kg are fired from the car with an initial velocity 100m//s at an angle 30^@ with the horizontal. The first cannon hall hits the stationary carriage after a time t_0 and sticks to it. Determine t_0 . At t_0 , the second cannon ball is fired. Assume that the resistive force between the rails and the carriage is constant and ignore the vertical motion of the carriage throughout. If the second ball also hits and sticks to the carriage, what will be the horizontal velocity of the carriage just after the second impact?

A car P is moving with a uniform speed 5sqrt3 m//s towards a carriage of mass 9 kg at rest kept on the rails at a point B as shown in figure. The height AC is 120 m. Cannon balls of 1 kg are fired from the car with an initial velocity 100m//s at an angle 30^@ with the horizontal. The first cannon hall hits the stationary carriage after a time t_0 and sticks to it. Determine t_0 . At t_0 , the second cannon ball is fired. Assume that the resistive force between the rails and the carriage is constant and ignore the vertical motion of the carriage throughout. If the second ball also hits and sticks to the carriage, what will be the horizontal velocity of the carriage just after the second impact?

Figure shows a metal rod PQ resting on the smooth rails AB and positioned between the poles of a permanent magnet. The rails, the rod, and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod =15 cm, B =0.50 T, resistance of the closed loop containing the rod 9.0 m Omega . Assume the field to be uniform. (a) Suppose K is open and the rod is moved with a speed of 12 "cm s"^(-1) in the direction shown. Give the polarity and magnitude of the induced emf. (b) Is there an excess charge built up at the ends of the rods when K is open ? What if K is closed ? (c) With K open and the rod moving uniformly, there is no net force on the electrons in the rod PQ even though they do experience magnetic force due to the motion of the rod. Explain. (d) What is the retarding force on the rod when K is closed ? How much power is required (by an external agent) to keep the rod moving at the same speed (= 12 cm s^(-1) ) when K is closed ? How much power is required when K is open? (f)How much power is dissipated as heat in the closed circuit ? What is the source of this power ? (g) What is the induced emf in the moving rod if the magnetic field is parallel to the rails instead of being perpendicular ?

Figure 6.20 shows a metal rod PQ resting on the smooth rails AB and positioned between the poles of a permanent magnet. The rails, the rod, and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = 9.0 m Omega . Assume the field to be uniform. (a) Suppose K is open and the rod is moved with a speed of 12 cm s^(-1) in the direction shown. Give the polarity and magnitude of the induced emf. (b) Is there an excess charge built up at the ends of the rods when K is open? What if K is closed? (c) With K open and the rod moving uniformly, there is no net force on the electrons in the rod PQ even though they do experience magnetic force due to the motion of the rod. Explain. (d) What is the retarding force on the rod when K is closed? (e) How much power is required (by an external agent) to keep the rod moving at the same speed (=12 cm s^(-1) ) when K is closed? How much power is required when K is open? (f ) How much power is dissipated as heat in the closed circuit? What is the source of this power? (g) What is the induced emf in the moving rod if the magnetic field is parallel to the rails instead of being perpendicular?

An electron beam after being accelerated from rest through a potential difference of 500 V in vacuum is allowed to impinge normally on a fixed surface. If the incident current is 100muA , determine the force exerted on the surface assuming that it brings the electrons to rest. (e=1.6xx10^(-19)C,m=9.0xx10^(-31)"kg")

Niels Bohr a Danish physicist received his PhD from the University of Copenhagen in 1911. He that spent a year with J.J. Thomson and Ernest Rutherford in England. In 1913, he returned to Copenhagen Where he remained for the rest of his life. In 1920 he was named Director of the Institute of theory! Physics After first World War Bohr worked energetically for peaceful uses of atomic energy recieved the first Atoms for Peace award in 1957 Bohr was awarded the Nobel Prize in Physics 1922 (a) The Angular momentum of an electron in a given stationary state can be expressed as m_e vr =h/(2pi) where n=1, 2,3 ...... Thus an electron can move only in those orbits for which its angular momentum is integral multiple of h/2 pi that is why only certain fixed orbits are alowed (b) The radii of the stationary states are expressed as r_n=n^2a_0 where a_0 =52.9 pm. Thus the radius the first stationary state, called the Bohr radius, is 52.9 pm. Normally the electron in the hydrogen atom is found in this orbit (that is n =1). As n increases the value of r will increase (c) The most important property associated with the electron E_n=-2.18xx10^(-18)(Z^2/n^2)J n=1,2,3 (d)it is also possible to calculate to calculate the velocities of electrons moving in these orbits by using v_n=2.18 10^6xxZ/n m/sec. Qualitatively the magnitude of velocity of electron increases with increase of positive charge on the nucleus and decreases with increases the value of n. (e)Bohr's theory can also be applied to th ions containing only one electron, similar to that present it hydrogen atom. For example , He^+ Li^(2+) , Be^(3+) and so on. given by the expression Ex=-218x n=1,2,3 (d) It is also possible to calculate the velocities of electrons moving in these orbits by using V 2.1810 cm/sec Qualitatively the magnitude of velocity of electron increases with increase of positive charge on the nucleus and decreases with increase the value of n (e) Bohr's theory can also be applied to the ions containing only one electron, similar to that presenti hydrogen atom For example, Help, Be and so on Choose the correct statement