# Two identical balls and , each of mass 2 kg and radius , are suspended vertically from inextensible strings as shown in Fig. The third ball of mass 1 kg and radius falls and hits and symmetrically with 10 m/s. Speed of both and just after the collision is 3 m/s Speed of just after collision is a) 2 m/s b) m/s c) 5 m/s d) ## Question ID - 101124 :- Two identical balls and , each of mass 2 kg and radius , are suspended vertically from inextensible strings as shown in Fig. The third ball of mass 1 kg and radius falls and hits and symmetrically with 10 m/s. Speed of both and just after the collision is 3 m/s Speed of just after collision is a) 2 m/s b) m/s c) 5 m/s d) 3537

(a)

First calculate, As the ball and are constrained to move horizontally (immediately after collision), if ‘ ’ be the impulse imparted by ball ‘ ’ to each of and , the impulse received by ball from them would be  Now, each of ball and received impulse ‘ ’ as shown in Fig., but moves horizontally as its vertical comp. gets balanced by impulse imparted to ball and by the respective strings and hence,  magnitude of impulse)

Now, for ball , if its final velocity is downwards, we have   sign indicates that it is directed upwards)

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