
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 ...

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 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). ...

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 ...

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 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 ...

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 ...

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 ...

How to calculate inclination angle when both x as well as y coordinates of the target is given (in projectile motion)? (as well as initial velocity) ...

A CHAIN CONSISTING OF 5 LINKS OF MASS 0.1 KG IS LIFTED VERTICALLY WITH A CONSTANT ACCELERATION OF 2.4 m/s^2 .THE FORCE OF INTERACTION BETWEEN THE TOP LINK AND LINK IMMEDIATELY BELOW IT WILL BE : 1) 6.15 N 2) 4.92 N 3) 9.84 N ...

A uniform chain of mass m hangs from a light pulley,with unequal lengths of the chain hanging from the two sides of the pulley.The force exerted by the moving chain on the pulley is (a)mg (b)>mg (c)<mg (d)either (b) or ...

Work done by a body in lifting a block upto a height 7 is a) positive b) negative c) zero d) none ...

A rod OA of mass m and length L hinged at end O can rotate smoothly in vertical plane about horzontal axis passing through O .It is released from a horizontal position as shown. and strikes a block of mass M kept vertically b ...

A body starts from rest with uniform acceleration. If its velocity after n second is upsilon , then its displacement in the last two seconds is a) frac{2upsilon left( n+1 ight)}{n} b) frac{upsilon left( n+1 ight)}{n} c) frac{ ...

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If the body covers onethird distance at speed v1, next one third at speed v2 and last one third at speed v3, then average speed will be a) frac{{{upsilon }_{1}},{{upsilon }_{2}}+{{upsilon }_{2}},{{upsilon }_{3}}+{{upsilon }_ ...

A car A is travelling on a straight level road with a uniform speed of 60 km/h. It is followed by another car B which is moving with a speed of 70 km/h. When the distance between them is 2.5 km, the car B is given a decelerat ...

A carrom board (having dimension 4ft * 4ft) has the queen at the centre. The striker hits the queen,which moves to the front edge,rebounds and finally enters the hole behind the striking line. Find the displacement of the que ...

Using vectors prove that : *Image* the coordinates of C is (x1+x2,y1+y2) Given : the coordinates of A are (x2,y2) and the coordinates of B are (x1,y1) and OACB is a parallelogram (Y and X represent the coordinate axes) ...

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Two seconds after projection a projectile is travelling in a direction inclined at 30Â° to the horizontal.After one more second it is travelling horizontally.Determine the magnitude and direction of its velocity. ...

At time t=0 string A is cut, then what will be the maximum compression in the spring if spring constant is K.(Assume surfaces are smooth and initially spring was at its natural length) *Image* ...

Mass of each block is 1 Kg. Find the minimum value of F so that sliding occurs at both the surfaces. *Image* ...

*Image* I have a lenghty solution,but if anyone can give a shortcut method for this? ...

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*Image* please post the solution ...