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**momentum word problem....**

Problem:

A tennis ball initially moves with a velocity of 30.0 m/s

horizontally to the right. A tennis racket strikes the ball,

giving it a velocity of 30.0 m/s to the left. Treat the

collision as elastic and the ball and racket as particles of

mass 0.0500= m1 kg and 0.500= m2 kg respectively.

Find the initial velocity of the racket:

__My solution:__

I'm going to use the equation:

Final (V) Ball = (m1 - m2) / (m1 + m2) * Ball(Vi)

The racket is going some initial speed Vi... but because this equation requires that the second object , the racket, be stationary I will assign a new speed for the ball... 30 + Vi,

then solve for Vi

-30 = (0.0500 - 0.500)/( 0.0500 + 0.500) * (30 + Vi)

-30/((0.0500 - 0.500)/( 0.0500 + 0.500)) - 30 = Vi = -6.66 m/s

However the answer in the book is... -3.00..

Some help please..... thank you.