
In the Bohr model of a hydrogen atom, the centripetal force is furnished by the coulomb attraction between the proton and the electron. If {{a}_{0}} is the radius of the ground state orbit, m is the mass, e is the charge on t ...

An element having b atomic no and a mass no. under goes a α emission then a β emission simultaneously .. then the new values of atomic and mass no. is a) a2, b4 b) a4,b1 c) a4,b2 d) none ...

A 50N object was lifted 2.0 m vertically and is being held there.Â How much work is being done in holding the box in this position? a) more than 100 J b) 100 J c) less than 100 J, but more than 0 J d) 0 J ...

A pump draws water from a tank and issues it from the end of a horse which is 2.5m vertically above the level from which the water is drawn. The cross sectional area of the hose is 10cm^{2} , and the water leaves the end of t ...

A force vec{F}=2hat{i}3hat{j}+4hat{k} (N) acts on a particle which undergoes a displacement vec{r}=7hat{i}+3hat{j}2hat{k} (M). Calculate the work done by the force a) 37 J b) 9 J c) 49 J d) 14 J ...

A bulb is made using two filaments. A switch selects whether the filaments are used individually or in parallel. When used with a 15 V battery, the bulb can be operated at 5 W, 10 W or 15 W. What should be the resistances of ...

An object is lifted vertically 2.0 m and held there.Â If the object weighs 90 N, how much work was done in lifting it? a) 360 J b) 180 J c) 90 J d) 0 J ...

Condenser A has a capacity of 15 when it is filled with a medium of dielectric constant 15. Another condenser B has a capacity 1 with air between the plates. Both are charged separately by a battery of 100V. After charging, b ...

why does potential drop across a capacitor????? ...

Determine the capacitance of a system consisting of a metal ball of radius a and an infinite conducting plane separated from the centre of the ball by the distance b if b>>a. ...

A particle is projected with velocity 2âˆš(gh) so that it just clears two walls of height h which are at a distance of 2h apart from each other. Prove that the time of passing between the two walls is 2âˆš(h/g). ...

I am stuck up with another question. During iceskating,why are no tracks left behind after the skier passes? Anyone care to help me out? Thanks in advance. I need it urgently,as my exam is on Tuesday. ...

Two objects of masses 1 x 103 kg and 4 x 103 kg have equal momentum. What is the ratio of their kinetic energies? a) 4:1 b) 2:1 c) 16:1 d) √2:1 ...

An electric dipole is placed in an electric field generated by a point charge a) The net electric force on the dipole must be zero b) The net electric force on the dipole may be zero c) The torque on the dipole due to the fie ...

The capacity of a parallel plate condenser is . If a dielectric of relative permitivity and thickness equal to one fourth the plate separation is placed between the plates, then its capacity becomes C. The value of will be a) ...

The graph between the displacement x and time t for a particle moving in a straight line is shown in figure. During the interval OA, AB, BC and CD, the acceleration of the particle is *Image* a) (+, 0, +, +) b) (, 0, +, 0) c ...

Â While running if we want to stop suddenly we fall down because. a) Inertia of rest b) Inertia of Motion c) data insfficient d) none ...

The ratio of an angular speed of hours hand and seconds hand of a clock is a) 1:1 b) 1:60 c) 1:720 d) 3600:1 ...

A sphere of 4 cm radius is suspended within a hollow sphere of 6 cm radius. The inner sphere is charged to a potential 3 e.s.u. When the outer sphere is earthed. The charge on the inner sphere is a) 54 e.s.u. b) frac{1}{4}, e ...

Velocity and Speed will be equal if a) Time of motion is equal b) Distance=Displacement c) Not possible d) None ...

An unknown cell balances 300 cm of wire in a potentiometer circuit, but the balance length reduces to 280 cm when a resistance of 28 ohm is added in parallel with the cell.A standard cell of emf 1.1V balances 220 cm on the sa ...

A body moves with speed 20m/sec for 10 sec and then with 30m/sec for some distance. The average speed may be (A) 8m/sec (B) 15m/sec (C) 25m/sec (D) all of these are possible ...

Work done by friction while we are walking is zero because: a) The point of application does not move. b) No friction is acting. c) The direction of friction and direction of walking are different. d) None of the above. ...

Â A work of 4900j is done on road of mass 50 kg to lift it to a certain height. Calculate the height through which the load is lifted. a) 10 b) 20 c) 30 d) none ...

2 bodies of equal masses has momentum in the ratio 3:1. Then the ratio of their momentum is a) 1:3 b) 3:1 c) *Image* d) None of them ...

A cylindrical pulley of mass M and radius R is connected to another pulley of mass M/2 ,R/2 through a massless string as shown. If sufficient string is wrapped over larger pulley,find the accleration of mass M attached to the ...

The mass of a body id 5kg and its acceleration is 4m/s2 a) 30N b) 20N c) 40N d) None of these ...

Ratio of the SI to the CGS unit of force is a) 105 : 1 b) 1 : 105 c) 103 : 1 d) None of these ...

Force is also defined as the product of a) Mass and velocity b) Velocity and Acceleration c) Mass and acceleration d) None ...

A body of mass 2 kg is moving with a velocity 8 m/s on a smooth surface. If it is to be brought to rest in 4 seconds, then the force to be applied is a) 8N b) 4N c) 2N d) 1N ...