YAPHT: physics help, friction coefficients

[MikeMike]

Masses m1=10.0kg, and m2=5.0kg are connected by a light string that passes over a frictionless puller. if, when then system starts from rest, m2 falls 1.00m in 1.2s, determine the coefficient of kinetic friction between m1 and the table.


well i get an answer of 3.16, however the book has an answer of 2.88

i am not sure where my formula went wrong.

my final formula turned out to be

(funy mew symbol)Ff=Fw-m1a-m2a

fw1=49n, or m2g which is 5x9.8

so the final value for Ff= (Fw1-m1a-m2a)Fw2

is my formula wrong???? if so where?

help??????

edit: i guess i should say, i used 1.12 m/s^2 for a.

MIKE

 

[TuxDave]

Originally posted by: nourdmrolNMT1
Masses m1=10.0kg, and m2=5.0kg are connected by a light string that passes over a frictionless puller. if, when then system starts from rest, m2 falls 1.00m in 1.2s, determine the coefficient of kinetic friction between m1 and the table.


well i get an answer of 3.16, however the book has an answer of 2.88

i am not sure where my formula went wrong.

my final formula turned out to be

(funy mew symbol)Ff=Fw-m1a-m2a

fw1=49n, or m2g which is 5x9.8

so the final value for Ff= (Fw1-m1a-m2a)Fw2

is my formula wrong???? if so where?

help??????

edit: i guess i should say, i used 1.12 m/s^2 for a.

MIKE

For starters, the equation for you acceleration is distance = 0.5*acceleration*time^2. 1m=0.5*x*1.2s^2 => x = 1.388889m/s^2 That should correct things.

 

[AbsolutDealage]

YADMHFMT

"Yet Another Do My Homework For Me Thread"

 

[dmw16]

2.88 is a very odd answer for coeff. of friction. Normally is it lower than 1. I ran through the numbers and got .288. That seems more resonable and also, being off by a decimal place means I'm not totally off. It goes like this...

for mass2: Yfinal = .5*a*(1.2)^2
so a=1.389ms^-2
that means acceleration for the total system is 1.389ms^-2

therefore
Mtotal*a = Ftotal

Ftotal = Mass2*g - Mass1*(mew)*g

solve it out and get mew = .288

That seems resonable
-doug

 

[MikeMike]

Originally posted by: AbsolutDealage
YADMHFMT

"Yet Another Do My Homework For Me Thread"

yafu

hey, i tried it mutha***** i got an answer that wasnt right and so i came on here to see what i did wrong.

and yea its supposed to be .288. so im way off some where. im gunna check with what you guys had and see where i messed up my equation.

ok so it seems that the 1.39 made a decent difference, and brought me down to .301. that seems reasonably close to what is necessary, just not sure whe i keep getting that?

and (name of person above me) did you mean M1G or M1A

cuz m1g makes the number negative.

MIKE