physics point

  Q/1. If in an elastic collision, a massive particle collides against a lighter One at rest ? (a) it can never bounce back along its original path   (b) it may bounce back along its original path (c) the two particles move at right angles to each other after collision   (d) None of the above Ans : P before collision =   mu     but v = - u     P after collision = mv   ∆ P   = mu – (-mu) = 2mu Option (a) is correct Q/2. In one-dimensional elastic collision of two particles, the ratio of velocities of separation and approach is equal to ? (a) coefficient of restitution                (b) negative of coefficient of restitution   (c) zero, if collision is perfectly elastic (d) infinite   Ans :   coefficient of restitution ;   e = (v 2 -v 1 )/(u 2 – u 1 )   Q/3. In which of the following conditions, the tot...

  Q/1. An object is dropped on a cushion from a height 10m above it. On being hit, the cushion is depressed by 0.1 m . Assuming that the cushion provides a constant resistive force, the deceleration of the object after hitting the cushion, in terms of the acceleration due to gravity g is ?   (a) 10 g                (b) 50 g              (c) 100 g                 (d) g Ans :   From conservation at energy                           mgh =   mv 2 /2               ⇒   v = √ (20g)   The equation at motion when partition the cushion        ...

  Q/1. For an electron in a one-dimensional infinite potential well of width 1 Å, calculate (i) the separation between the two lowest energy levels; (ii) the frequency and wavelength of the photon corresponding to a transition between these two levels ?   Ans : (i)     E n = π 2 ђ 2 n 2 / 2ma 2     ;     2a = 1Å               E 2 – E 1 = (4 -1) π 2 ђ 2 / 2ma 2                            = 3*π 2 (1.055-10 -34 ) 2 / 8*9.1*10 -31 *10 -20                          = 1.812*10 -17 J = 113.27 eV       (ii) h ν = E 2 – E 1 = 1.812*10 -17 J               ...