# Two balls of masses  and  are suspended from point  by two equal inextensible threads, each of length  m. Ball of mass  is drawn aside and held at the same level as  but at a distance  from , as shown in Fig. When ball  is released, it collides elastically with the stationary ball of mass Velocity with which the ball of mass  collides with the other ball is 1 m/s b) 2 m/s c) 3 m/s d) 4 m/s

## Question ID - 101265 :- Two balls of masses  and  are suspended from point  by two equal inextensible threads, each of length  m. Ball of mass  is drawn aside and held at the same level as  but at a distance  from , as shown in Fig. When ball  is released, it collides elastically with the stationary ball of mass Velocity with which the ball of mass  collides with the other ball is 1 m/s b) 2 m/s c) 3 m/s d) 4 m/s

3537

(d)

Ball of mass  falls freely till thread becomes taut. At that instant inclination  of the thread with the vertical be given by

Ball of mass  falls freely through height

Velocity of this ball at this instant is

It can be resolved into two components

i. , along the thread. But thread is inextensible, hence this component decreases to zero (due to tension developed in the thread)

ii. , perpendicular to the thread. Due to this component ball starts to move along a circle whose centre is at

According to law of conservation of energy,

Kinetic energy of ball  just before collision = Its kinetic energy at  + Further loss of its potential energy

According to law of conservation of momentum,

And coefficient of restitution,

Substituting and

the height to which it rises is

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Following question is based on analogy.  There are two pairs of letters combination in each question.  The first (left hand side) pair has some relationship between its members.  In the second pair, one member is missing.  Find this out from the options such that this pair has similar relationship as the first pair.

 PRINCIPAL : LAPICNIRP : : ADOLESCENCE : ? (a) ECNCESELODA (b) ECNECSLEODA (c) ECNSCEELODA (d) ECNECSELODA