A black ball of mass 2kg moving at velocity of 10 m/sec collides with a stationary white ball of mass 3kg find their common velocity if they stick together after collision?

4 m/s

Explanation:

here

mass of black ball (m1) = 2 kg

initial velocity of black ball (u1) = 10 m/s

mass of white ball (m2) = 3 kg

since white ball is stationary so initial velocity of white ball (u2) = 0 m/s

let v be the common velocity then

by the principle of linear momentum

linear momentum before collision = linear momentum after collision

or, m1u1 + m2u2 = (m1+m2)v [becoz they have common velocity v after collision]

or, v = (m1u1 + m2u2)/m1+m2

or, v = (2*10 + 0)/2+3

or, v = 20/5

~ v = 4 m/s

the purpose of the heading in the passage is to identify who is telling the story.

this excerpt is part of the book sugar changed the world (2010) written by marc aronson and marina budhos. as the book has been written by two people, the heading "marc" indicates that this specific excerpt is being narrated by aronson. in the fragment, marc describes his grandfather's story after hearing it from his cousin. however, there are other excerpts where budhos is the one that tells the story of her family.

aronson and budhos, who are husband and wife in real life, decided to write sugar changed the world when they found out how sugar, which had an important role in slavery and economy, changed their ancestors' lives.