1.

A ball of mass m moving at a speed v makes a head-on collision with an identical ball at rest. The kinetic energy of the balls after the collision is three fourths of the original. Find the coefficient of restitution.

Answer»

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ANSWER::


Mass of FIRST ball = m

Speed of first ball = v

Mass of SECOND ball = m


Let final velocities of first and second ball are v₁ and v₂ respectively.


Using law of conservation of momentum,


m(v₁ + v₂) = mv


v₁ + v₂ = v Equation 1


And , v₁ - v₂ = ev Equation 2


Given:-


Final KINETIC Energy = 3/4 Initial Kinetic Energy


(1/2)mv₁² + (1/2)mv₂² = (3/4) x 1/2 mv²


v₁² + v₂² = (3/4) v²


[(v₁ + v₂)² + (v₁ - v₂)² ] / 2 = 3v² / 4


(1 + e²)v² / 2 = 3v² / 4


1 + e² = 3/2


e² = 1/2


e = 1 / √2


Hope it helps!



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