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A ball with a mass of #5kg# moving at #2 m/s# hits a still ball with a mass of #9 kg#. If the first ball stops moving, how fast is the second ball moving?

Answer 1

#1.111 \ \text{m/s}#

One ball of mass #m_1=5#kg moving at #u_1=2\ m/s# hits another ball of mass #m_2=9# kg at rest #u_2=0#. After collision, the first ball stops i.e. #v_1=0# & second ball moves with a velocity of #v_2# in the initial direction of first ball then

By the conservation of momentum in moving direction of first ball

#\text{momentum before collision}=\text{momentum after collision}#

#m_1u_1+m_2u_2=m_1v_1+m_2v_2#

#5(2)+9(0)=5(0)+9v_2#

#9v_2=10#

#v_2=10/9#

#v_2=1.111 \ \text{m/s}#

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Answer 2

Benjamin Asiedu

The second ball will move at 1 m/s in the opposite direction.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.