Two bodies initially at rest, started moving towards each other due to mutual attraction. Which of the following is incorrect ?

Options

A. `vec(a)_(cm) = 0`
B. `Sigma Delta vec(P) = 0`
C. `vec(v)_(cm) =` constant
D. None of these

Answer

D

Explanation

as `(vec(F)_("net"))_("ext.") = 0`, so `vec(a)_(COM) = 0` because `(vec(F)_("net"))_("ext.") = M vec(a)_(COM)`
[ `:.` Newton's `2^(nd)` law of motion]
As initially `vec(v)_(COM) = 0`
so `vec(P)_("system") = Sigma vec(Delta)p = M vec(v)_("COM") = 0`
As `vec(v)_(COM)` remains 0 always,
so `vec(v)_(COM) =` constant.