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Two equal spheres  and , each of mass , are in contact on a smooth horizontal table. A third sphere  of same size as that of  or  but mass  impinges symmetrically on them with a velocity  and is itself brought to rest

The coefficient of restitution between the two spheres  and  (or between  and ) is

a)

b)

c)

d)



Question ID - 101219 | SaraNextGen Top Answer

Two equal spheres  and , each of mass , are in contact on a smooth horizontal table. A third sphere  of same size as that of  or  but mass  impinges symmetrically on them with a velocity  and is itself brought to rest

The coefficient of restitution between the two spheres  and  (or between  and ) is

a)

b)

c)

d)

1 Answer
127 votes
Answer Key / Explanation : (a) -

(a)

 velocity of sphere  before impact. As the spheres are identical, the triangle  formed by joining their centres is equilateral. The spheres  and  will move in direction  and after impact making an angle of  with the original lines of motion of ball

Let  be the speed of the ball  and  after impact

Momentum conservation gives

 (i)

From Newton’s experimental law, for an oblique collision, we have to take components along normal, i.e., along  for balls  and

Combining Eqs. (i) and (ii), we get

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