# Can u solve this??????puzzle a marble going at a speed of 2ms inverse 1 hits another marble of equal mass at rest.if the collision is perfectly elastic,then the velocity of the first marble after collision is 1.4ms-1(read as inverse 1) 2.0ms-1(read as inverse 1) 3.2ms-1(read as inverse 1) 4.3ms-1(inverse 1) .,,,,,,,plzz do it with full steps.......need it quickly.....plzz help!!!!if posssible

1

2015-09-12T05:13:58+05:30

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Option 2..
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we apply conservation of linear momentum and also the conservation of kinetic energy, as the collision is elastic.  There is no loss of energy.

m * u + m * 0 = m * v1 + m * v2
=>  u = v1 + v2  -- (1)

1/2  m * u²  + 0 = 1/2 m * v1²  + 1/2 m * v2²
=>   u² = v1² + v2²
=>  u² = (u - v2)² + v2²
=>  -2 u v2 + 2 v2² = 0
=>  v2 = 0  or    v2 = u
Then,  v1 =  u  or    v1 = 0

Here it is not possible that  v1 = u and v2 = 0, as the marble 1, cannot collide and run over the marble 2 and still have marble 2 at rest.

Thus  v1 = 0 and  v2 = u.    So answer is  (2).

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