413 - Physics Questions Answers

Plz help sir
Asked By: DARIUS
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Plzz solve all the intigrations step by step ☺️☺️☺️.plzz
Asked By: ASHLOK
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Consider an electron trapped in an infinite well whose width is 98.5 pm. If it is in a state with n = 15, what are (i) its energy? (ii) the uncertainty in its momentum? (iii) the uncertainty in its position?

Asked By: ANKIT SONI
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Joshi sir comment

Let width=b For nth state nλ2=b λ=2bn Now E =p22m = (hλ)22m Solve after putting the value of λ  Uncertainty in position=b Now use p.x = nh/2π for finding uncertainty in momentum 

A solid conducting sphere of radius R is placed in a uniform electric field E as shown in figure-1.441. Due to electric field non uniform surface charges are induced on the surface of the sphere. Consider a point A on the surface of sphere at a polar angle θ from the direction of electric field as shown in figure. Find the surface density of induced charges at point A in terms of electric field and polar angle θ.

 

 

Asked By: DEBRAJ SAHA
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Joshi sir comment

To nullify the electric field inside, the conducting sphere creates a situation in which electric field inside due to charge on sphere would be same as that of given electric field. Now this is the case, which is same as Irodov 3.17.

See the video now

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FinallyE = σ03ε0 = σ3ε0cosθ Now solve

Any method that can be used other than superposition principle? 
Asked By: LUFFY
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Joshi sir comment

By superposition principle, it is solved in minimum time and effort, other method is very complex. So use superposition principle.

Divide current in point 1 and 2, considering symmetry throughout, we get the equivalent resistance of the whole network except resistor R between 1 and 2 is 2R

Now 2R and R in parallel between 1 and 2

Now solve

 

  

A cylindrical pipe of radius r is rolling towards a frog sitting on the horizontal ground. Center of the pipe is moving with velocity v. To save itself ,the frog jumps off and passes over the pipe touching it only at top. Denoting air time of frog by T, horizontal range of the jump by R and acceleration due to gravity by g. Find T and R.

Asked By: MUDIT
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According to given condition 2r = uy2/2g, T= 2uy/g =24gr/g=4r/g At top point due to touch, vecocity of the frog be ux2v. R=[uxuy/g]+[ux2v)uy/g]=[uy/g](2ux2v) =[2uy/g](uxv) =T(uxv) Now minimum possible value of velocity of frog at top to  cross the cylinder is gr (By the concept of vertical circle) now solve carefully without error

Physics >> Optics >> Refraction IIT JEE
Asked By: BHASKAR JHA
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Joshi sir comment

Let α is small angular displacement As shown x = lsinα and y = lcosα/μ now use sin2α+cos2α = 1

A particle of mass m = 2kg is placed on the top of a hemisphere of M 4 kg. The hemisphere is placed on smooth ground. The particle is displaced gently. Then ratio of normal and pseudo force(seen from hemisphere frame) acting on particle when theta = 30 degree. Assume particle remain in contact with hemisphere.

Asked By: GUDDU KUMAR
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Joshi sir comment

Let the acceleration of hemisphere is ah N sinθ = Mah N/mah = M/msinθ  Here pseudo force is considered due to acceleration of hemisphere 

a small ball of mass 1kg and a charge 2/3 uC is placed at the center of a uniformly charged sphere of radius 1m and charge 1/3 mC. a narrow smooth horizontal groove is made in the sphere from centre to surface as shown in figure. the sphere is made to rotate about its vertical diameter at a constant rate of 1/2pi revolutions per second. find the spedd w.r.t ground with which the ball slide out from the groove. neglect any magnetic force acting on ball?

Asked By: VISHNU VARDHAN
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Joshi sir comment

Potential difference from centre to surface = 3V/2 - V = V/2 here V = kq/r (q is charge of sphere) mvr2/2 = VQ/2 (Q is charge of particle) vr is radial velocity Besides tangential velocity due to rotation of sphere = rω=r2πn now solve  

A small ball is thrown from foot of a wall with minimum possible velocity to hit a bulb B on the ground at a distance L away from the wall.Find the expression for height h of shadow of the ball on the wall as a function of time t.Acceleration due to gravity is g.

Asked By: MUDIT
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