Homework Help: physics

Posted by bill on Thursday, September 9, 2010 at 2:30pm.

You are trying to slide a refrigerator across a horizontal floor. The mass of the refrigerator is 199 kg, and you need to exert a force of 343 N to make it just begin to move.
(a) What is the coefficient of static friction between the floor and the refrigerator?

F=(mu)m*g
343\1950.2= mu
mu=.17 BUT ITS WRONG!
WHAT AM I DOING?

(b) After it starts moving, the refrigerator reaches a speed of 1.9 m/s after 4.5 s. What is the coefficient of kinetic friction between the refrigerator and the floor?
v = u + at

u =0

1.9 = 4.5 x a

a = 0.422 m/s^2

AND THATS WRONG???????????????????

physics - bobpursley, Thursday, September 9, 2010 at 3:29pm
I get .1758, to three significant digits. .176

On the second: find a

a= (1.9-0)/4.5 m/s^2=.42 m/s^2

Now, netforce= friction+ma
friction=netforce-ma
mu*mg=343N-199*.422
solve for mu.

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