Particle Momentum Conservation in a Two-Particle System

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In a two-particle system with mass m, connected by a string, the first particle is projected with velocity u, leading to a calculated speed of the second particle as u/2 when projected along the string. The confusion arises from the mention of two answers: u/2 for speed and mu/2 for momentum, highlighting a misunderstanding of units. The discussion emphasizes that only the first answer represents speed, while the second is incorrectly presented as momentum, which should not be the case when velocity is requested. Participants express frustration over textbook inconsistencies and the importance of clarity in physics problems. The conversation underscores the need for accurate terminology in educational materials.
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6. Two particles, each of mass m, are connected by a light inextensible string of length 2l. Initially they lie on a smooth horizontal table at points A and B distant l apart. The particle at A is projected across the table with velocity u. Find the speed with which the second particle begins to move if the directions of u is.
(a) along AB,

mu = (m+m)v
v = u/2

But the given answer is u/2 and mu/2. Can anyone explain to me why there are 2 answers? Thanks.
 
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frozen7 said:
But the given answer is u/2 and mu/2.
Only the first answer is a speed; the other is a momentum.
 
I can't see the answer of \frac{1}{2}mu being correct, because that would leave the velocity having units of m\cdot kg \cdot s^{-1}, which doesn't happen.
 
Thanks..I am so stupid...
 
It really is bad practise by a book to ask for a velocity then give an answer in momentum. I've just had some problems with a textbook myself ...:mad:
 

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