physics
posted by kim on .
A mass m1 = 10 kg on top of a rough horizontal table surface is connected by a massless cable over a frictionless wheel to a hanging mass m2 = 5 kg, as shown in the previous problem. In m2 falls 1 m from rest in 1.2 seconds, find the coefficient of kinetic friction between m1 and the table surface.
also,
A mass m1 = 10kg resting on a rough horizontal table surface is connected by a massless cable over a frictionless wheel to a hanging mass m2= 5 kg,. What is the minimum coefficent of static friction which will allow the masses to remain at rest?

1.
h=at²/2
a=2h/t²= 2•1/1.2²=1.4 m/s²
m2•a =m2•g –T = > T = m2•gm2•a.
m1•a=TF(fr) = Tμ•N= Tμ•m1•g = m2•gm2•a μ•m1•g.
μ=[m2•g – a(m1+m2)]/m1•g = [5•9.8 – 1.4•15]/10•9.8 = 0.27.
2.
0 = m2•g –T
0=TF1(fr) = T μ(s) •m1•g
m2•g = μ(s) •m1•g,
μ(s) = m2/m1=5/10 = 0.5