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Homework Statement
a mass m1 is attached to a second mass m2 by an acme (massless, unstretchable) string. m1 sits on a table with which it has coefficients of static and dynamic friction μs and μk respectively. m2 is hanging over the ends of a table, suspended by the taut string from an acme pulley. at time t=0 both masses are released.
1. what is the minimum mass m2,_{min} such that the two masses begin to move?
2. If m2= 2m2,_{min}, determine how fast the two blocks are moving when mass m2 has fallen a height H (assuming the m1 hasn't yet hit the pulley)?
Homework Equations
Σf=ma
fsmax=μs*fn
vf^{2}=vi^{2}+2aΔx[/B]
The Attempt at a Solution
for a:
I am not sure about how I understand the question, but what comes to my mind when reading ( Begin to move) is that still the system acceleration is zero and that they are asking for the F_{smax} (the maximum static friction) just before the system starts to move and the friction becomes Kinetic friction of Fk.
so:
for block m1
Σƒ= m*a=0
f_{smax}=T
μs*Fn= T
μs*m1g=T
now for block m2:
Σƒ=m*a=0
m2g=T
and by this m2g=μs*m1g so m2=(μs*m1g)/g
section b)
I guess since the mass of m2 is doubled, that here we will deal with the kinetic friction rather than the static friction.
since both are linked by a rope with the same pulley than they must have the same acceleration, and we should find it.
and after finding it then we will use this equation:
vf^{2}=vi^{2}+2aΔx
where vi= 0
so vf=√(2aΔx).
am I right??
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