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Grade Select GradeMechanics

Q. A PARTICLE IS DROPPED FROM A HEIGHT OF 20m ONTO A FIXED WEDGE OF INCLINATION 300. THE TIME GAP BETWEEN FIRST TWO SUCCESSIVE COLLISIONS IS( ASSUME THAT COLLISION IS PERFETCLY ELASTIC)-
  1. 2 sec
  2. 2(3)1/2 sec
  3. 4 sec
  4. 4(3)½ sec

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Profile image of Bharat Makkar
11 Years agoGrade Select Grade
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4 Answers

Profile image of Manabendra Nath Gaine
11 Years ago
4(3)½ sec.
Profile image of Bharat Makkar
11 Years ago
wrong answer. i desperately want the right answer along with a proper explaination
 
Profile image of shashi K Sharma
ApprovedApproved Tutor Answer11 Years ago
The answer should be 4 second.
Shift your axes along the incline and perpendicular to it. The ball will rebound at 20m/s and at an angle 60degree with the incline, your acc along incline is gSin30 and that along new y axis is -gCos30.
between two consecutive collisions Apply S = ut + 1/2at^2 along your new y axis, and put it zero. Use the equation strictly along new Y axis,. hence use u=20cos30 and a=-gCos30 strike out and get the answer.
Profile image of Bharat Makkar
11 Years ago
thanks !!!!! your ans is right