Chain-Horizontal Pull

A pile of chains is lying on a rough surface with coefficient of friction $0.5,$ and a constant force of $\SI{40}{\newton}$ pulls on one end of the chains, as shown. To the nearest integer, find the velocity $v$ $($ in $\si[per-mode=symbol]{\meter\per\second})$ with which the chain gets pulled at the instant when $\SI{4}{\meter}$ of its length is lying on the surface.

Details and Assumptions:

• The initial length of the chain lying on the surface is $\SI{2}{\meter}.$
• Acceleration due to gravity is $\SI[per-mode=symbol]{10}{\meter\per\second\squared}.$
• The mass of the chain is $\SI[per-mode=symbol]{2}{\kilo\gram\per\meter}.$