Question

A body is moving parallel to x-axis. What is its angular momentum!

Answer 1

A particle is moving along a straight line parellel to x -axis .
hence position vector ( r^ ) = b j^
b be some value,i.e the parallel distance from x axis
mass of body = m
velocity of body V^ = v i^
we know ,
angular momentum = m ( r^ x V^)
=m ( b j^ x v i^)
= -mbv k^

note :- I x j = k
so, j x i = - k