Question Number 20349 by Tinkutara last updated on 25/Aug/17
$$\mathrm{A}\:\mathrm{ball}\:\mathrm{rolled}\:\mathrm{on}\:\mathrm{ice}\:\mathrm{with}\:\mathrm{a}\:\mathrm{velocity}\:\mathrm{of} \\ $$$$\mathrm{14}\:\mathrm{ms}^{−\mathrm{1}} \:\mathrm{comes}\:\mathrm{to}\:\mathrm{rest}\:\mathrm{after}\:\mathrm{travelling} \\ $$$$\mathrm{40}\:\mathrm{m}.\:\mathrm{Find}\:\mathrm{the}\:\mathrm{coefficient}\:\mathrm{of}\:\mathrm{friction}. \\ $$$$\left(\mathrm{Given},\:{g}\:=\:\mathrm{9}.\mathrm{8}\:\mathrm{m}/\mathrm{s}^{\mathrm{2}} \right) \\ $$
Commented by Tinkutara last updated on 25/Aug/17
$$\mathrm{Just}\:\mathrm{tell}\:\mathrm{the}\:\mathrm{answer}.\:\mathrm{Is}\:\mathrm{it}\:\mathrm{0}.\mathrm{25}\:\mathrm{or}\:\mathrm{0}.\mathrm{5}? \\ $$
Commented by ajfour last updated on 25/Aug/17
$${faulty}\:{question},\:{not}\:{clear}\:{whether} \\ $$$${ball}\:{rolls}\:{or}\:{just}\:{slides},\:{what}\:{type} \\ $$$${of}\:{ball},\:{what}\:{radius}... \\ $$$${did}\:{it}\:{start}\:{rolling}\:{since}\:{beginning} \\ $$$${it}\:{should}\:{not}\:{stop},\:{friction}\:{wont} \\ $$$${even}\:{act}\:{then} \\ $$$${if}\:{it}\:{just}\:{slides}\:{then} \\ $$$$\mu{mgx}=\frac{\mathrm{1}}{\mathrm{2}}{mv}^{\mathrm{2}} \\ $$$$\Rightarrow\:\mu=\frac{{v}^{\mathrm{2}} }{\mathrm{2}{gx}}=\frac{\mathrm{196}}{\mathrm{2}×\mathrm{9}.\mathrm{8}×\mathrm{40}}\:=\:\mathrm{0}.\mathrm{25} \\ $$
Commented by Tinkutara last updated on 25/Aug/17
$$\mathrm{Thanks},\:\mathrm{0}.\mathrm{25}\:\mathrm{I}\:\mathrm{wanted}. \\ $$