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Finding mass within a pulley system. Finding coefficient of friction 
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#1
Oct1111, 12:18 AM

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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/s^{2}. Find the mass of object m1 A. 0.61kg B. 0.72kg C. 6.0kg D. 26kg For m1 I have: F_{N}=Fg. Fg=mg, so 39N. F_{T}0(no Ff)=ma . So F_{T} is 6.0N. And then I'm lost. 8. A 45kg toboggan and rider decelerate on level show at 0.53m/s^{2}. 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 F_{N}=Fg. Fg=mg so 441.45N(rounded to 2SD). F_{net}=ma so 24N. And then I'm lost. I know that μ=Ff/F_{N} Someone help me please! 


#2
Oct1111, 12:41 AM

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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.



#3
Oct1111, 12:44 AM

P: 18

I got the mass...I think. F_{T}=ma. 6.0N=m_{1}(9.81m/s^{2}) So m_{1}=0.6112kg
Now for the other one... 


#4
Oct1111, 12:58 AM

P: 18

Finding mass within a pulley system. Finding coefficient of friction
 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 


#5
Oct1111, 02:14 AM

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#6
Oct1111, 11:55 AM

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#7
Oct1111, 01:31 PM

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#8
Oct1111, 04:42 PM

P: 18

Fg1FT=ma Use the total mass of the system. The difference of force of gravity and tension on the rope would be the net force acting on the system. 


#9
Oct1211, 04:31 AM

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The question supplies all the information you need. You have a mass (M1 + M2) being accelerated. The force that is causing the acceleration is the weight of M1.
One equation, one unknown. 


#10
Oct1211, 04:44 AM

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#11
Oct1211, 11:15 AM

P: 18

Thanks for your help. I tend to overthink these things



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