# Finding mass within a pulley system. Finding coefficient of friction

by Serendipitydo
Tags: coefficient, friction, mass, pulley
 P: 18 Ok so I'm in college upgrading, and doing my physics 20. I have a hand in assignment due Wednesday and I can't for the life of me figure out these two questions. 6. The 4.0kg block shown accelerates across a frictionless horizontal table at 1.5m/s2. Find the mass of object m1 A. 0.61kg B. 0.72kg C. 6.0kg D. 26kg For m1 I have: FN=Fg. Fg=mg, so 39N. FT-0(no Ff)=ma . So FT is 6.0N. And then I'm lost. 8. A 45kg toboggan and rider decelerate on level show at 0.53m/s2. What is the coefficient of friction between the toboggan and the snow? A. 0.012 B. 0.054 C. 0.22 D. 0.53 I got that FN=Fg. Fg=mg so 441.45N(rounded to 2SD). Fnet=ma so 24N. And then I'm lost. I know that μ=Ff/FN Someone help me please!
 HW Helper Thanks P: 5,372 You have a combined mass of M1 + M2 being accelerated (together). Write an equation for the force that is needed to accelerate such a mass.
 P: 18 I got the mass...I think. FT=ma. 6.0N=m1(9.81m/s2) So m1=0.6112kg Now for the other one...
P: 18
Finding mass within a pulley system. Finding coefficient of friction

 Quote by Serendipitydo I got the mass...I think. FT=ma. 6.0N=m1(9.81m/s2) So m1=0.6112kg Now for the other one...

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Ok I think I solved it. Ff is Fnet in the direction of acceleration? So since it's decelerating, wouldn't it accelerate in the direction of the friction?

So Ff=ma
Ff=24N

μ=Ff/FN
μ=24N/441N
μ=0.05442
HW Helper
Thanks
P: 5,372
 Quote by Serendipitydo I got the mass...I think. FT=ma. 6.0N=m1(9.81m/s2) So m1=0.6112kg Now for the other one...
Not so fast. You haven't got this one right, yet. You must determine the force needed to accelerate the combined masses, since they accelerate together.
P: 18
 Quote by NascentOxygen Not so fast. You haven't got this one right, yet. You must determine the force needed to accelerate the combined masses, since they accelerate together.
But I only need the mass of the one.
Emeritus
HW Helper
PF Gold
P: 7,819
 Quote by NascentOxygen You have a combined mass of M1 + M2 being accelerated (together). Write an equation for the force that is needed to accelerate such a mass.
P: 18